The Biggest Mistake I Made in Speech Therapy When Correcting a Lisp

By Karen Krogg, M.S., CCC-SLP | Last Updated June 2026| Explains the types of lisps in speech therapy

I sat there wondering how to correct a lisp…

“Okay, hide your tongue behind your teeth,” I suggested. I was sitting in another speech therapy session with a student, trying to correct a frontal lisp. Unsuccessfully, I might add.

“Thhhhhhhh,” was the response. To be fair, my student HAD put his tongue behind his teeth. My directions had been followed to a tee. The result was a “dentalized” /s/.

Basically, a voiceless “th” that was stopped by the front teeth. It didn’t sound right. I fought the urge to lower my head into my hands in defeat.

This is the exact part of the movie where the director would yell, “CUT!” 

Seriously, though, face palm.

There is nothing more frustrating than trying to correct a frontal lisp or a lateral lisp (or if we want to be really specific here, an interdental lisp, addental lisp, lateral lisp, strident lisp, or palatal lisp… but more on that later).

And I was a new SLP, desperately wanting to figure out this “correcting a lisp thing”.

This post contains affiliate links, which means we could receive a commission if you click a link and purchase something that we have recommended.

If you are a Speech-Language Pathologist who absolutely dreads the word ‘lisp’, then this is the article for you.

This article is the ultimate guide for SLPs: it covers the different types of lisps, when to treat them, HOW to treat them, tongue placement elicitation techniques, cues, tools, and FAQs.

I’m a CCC-SLP with 15 years of experience in outpatient pediatric and school settings. I’ve taken specialized coursework in orofacial myology and treating speech sound disorders. The notes throughout this guide contain everything I’ve learned through CEU courses and my own clinical experience.

What Is a Lisp?

A lisp is a speech sound error involving difficulty with pronouncing specific sounds (sibilant sounds, typically “s” and “z”), often involving improper tongue placement and/ or airflow differences. Contributing factors of a lisp may include dental issues, negative oral habits (such as thumb sucking), or learned speech patterns.

When Should You Treat a Lisp?

Some lisps are considered to be developmentally appropriate. For example, an interdental lisp in young child is not yet a cause for concern. Sometimes, children outgrow this type of lisp without therapy.

In my professional opinion, I typically start treating a lisp around age 6, especially if the child is showing signs of frustration. Treating a lisp involves the child paying special attention to cues regarding lingual placement and airflow control.

It is important to note that lateral lisps are generally considered nondevelopmental. These types of lisps need specialized treatment from a Speech-Language Pathologist.

Types of Lisps in Speech Therapy

In this post, I’m focusing on 5 common lisps in speech therapy, including: interdental, addental/ dentalized, lateral, palatal, and strident.

And once I realized that, I started to understand how important it was to understand the different types of lisps.

This is because each type of lisp requires different cueing.

A student with an interdental lisp may need help moving the tongue back and up. A student with a lateral lisp needs reminders to lift the sides of the tongue, so they can direct the airflow forward. A student with a palatal lisp will actually need guidance to move the tongue slightly forward.

That was the piece I was missing early on.

I had tried Facebook groups, Google Searches, and colleague advice, but I still felt stuck. After lots of research and CEU courses, though, it’s like it’s all clicked (ugh, finally). I needed to explain in a SIMPLE way, WHERE and HOW my students needed to move their tongue.

After completing a 4-day orofacial myology training, I realized something. I had been skipping an important foundational piece: establishing normal resting posture.

I like to consider the resting posture in every lisp case, and address it when it seems to be impacting progress.

The importance of establishing normal resting posture before even working on speech was drilled into me when I took orofacial myology training, and that deserves a post of its own. 

Right now, though, I want to focus on how I explain tongue placement and tongue movement to my students when I am establishing /s/ in isolation.

And once I’ve explained that, it becomes a lot clearer why my “hide your tongue” statement really didn’t work.

For a “typical” /s/ and /z/, your tongue tip can be UP or DOWN.

However, the sides of your tongue must be elevated, and they need to touch the sides of the top teeth.

Basically, you need a way to funnel the air forward and out.

So knowing THAT, we can then consider where our students need to place their tongues. 

When we understand what TYPE of lisp they have, we can give better directional cues.

Reference: Articulatory and Phonological Impairments: A Clinical Focus, Third Edition. By Jacqueline Bauman-Waengler

Type of Lisp	What It Sounds Like	Tongue Position	Main Treatment Focus
Interdental Lisp	“thun” for “sun”	tongue flat and forward, pushing through/ between front teeth	proper placement of the tongue inside the mouth
Addental/ Dentalized Lisp	distorted /s/	tongue flat and resting against the back of the front teeth	move tongue positioning slightly
Lateral Lisp	slushy s	The sides of the tongue are flat, so the air escapes into the cheeks	establish central airflow
Palatal Lisp	s sounds like “sh”	The tongue is too far back into the palatal area	move tongue forward
Strident Lisp	whistling s	excessive groove or airflow distortion	refine airflow control

Interdental Lisp Example

When your student is demonstrating an interdental lisp (frontal lisp), the tongue is forward and between the teeth.

The result sounds like a “th” for an “s”. It would be like your student is saying “think” for “sink”.

Target Word	What Child Says or How It Sounds	What Went Wrong
sun	thun	The tongue is too flat and forward, pushing between the upper and lower front teeth

Addental Lisp Example

I sometimes call this a “dentalized lisp”. When this is happening, you aren’t seeing the tongue between the teeth like you are for an interdental lisp. Instead, the tongue tip is touching the back surface of the teeth (or at least it is too far forward), and the edges of the tongue are flat.

Target Word	What Child Says/ What It Sounds Like	What Went Wrong
soup	a muffled or dull /s/ (almost like a “th” inside the mouth)	The tongue is flat, and the tip is touching the back surface of the teeth

Lateral Lisp Example

When your student is demonstrating a lateral lisp, the sides of his tongue are flat.

Because the sides aren’t lifting, air is flowing freely into the cheeks. When that escaping air mixes with saliva, it results in a “slushy” sound.

A lateral lisp can be bilateral or unilateral (meaning air may be escaping on both sides or one side).

I read an old articulation textbook once, and Hilda Fisher described a lateral lisp as a “slushy L”. That made complete sense to me.

Oh, and you’ll want to read about this neat lateral lisp straw technique, all about using a straw to teach your student how to direct the airflow straight.

Target Word	What Child Says or How It Sounds	What Went Wrong
sun	a slushy or distorted s, described as a “slushy L” by Hilda Fisher	The sides of the tongue are flat, and the air escapes into the cheeks and mixes with saliva, resulting in a slushy sound

Palatal Lisp Example

When your student has a palatal lisp, the tongue tip is too far back- it’s in the palatal area. The resulting sound would be more like a distorted “SH” instead of “s”.

Target Word	What Child Says or How It Sounds	What Went Wrong
sun	shun	The tongue is too far back into the palatal area, and the tongue tip needs to move forward to “home”

Strident Lisp Example

This is when /s/ sounds “whistle-like”- and it’s because too much airflow is being pushed through a narrow opening.

Target Word	What Child Says or How It Sounds	What Went Wrong
sun	The /s/ sounds like a whistle	Airflow may be too forceful, too narrow, or poorly controlled

Explaining Tongue Movement

“Hide your tongue.”

I think this is a common thing that is said to students when correcting a lisp- but hopefully the information above will detail why I don’t think this will result in a crisp /s/ or /z/.

The truth is, “hiding the tongue” will probably place the tongue directly behind the front teeth- and that’s going to result in an “addental” production of /s/. This has been my clinical experience.

Instead, I’d recommend trying to figure out what type of lisp your student has, so that you can better direct them to move their tongue to the right area.

How To Treat a Lateral Lisp

LATERAL LISP: “Oops- I heard slushy air. Make sure to lift the sides of your tongue,” I might tell my student who is demonstrating a lateral lisp. I know the “tunnel” wasn’t working because air flowed freely into the cheeks.

How To Treat a Dentalized Lisp

ADDENTAL OR DENTALIZED LISP: “Try moving that tongue tip up just a little,” I often say to my student who demonstrates an addental lisp.

How To Treat an Interdental Lisp

INTERDENTAL LISP: “Move your tongue tip in and UP towards home,” I might direct my student with an interdental lisp. “I saw your tongue come between your teeth!”

How To Treat a Palatal Lisp

PALATAL LISP: “Slide your tongue tip forward, towards home (the alveolar ridge), just a little,” I could suggest if my student is demonstrating a palatal lisp. “It’s too far back.”

How To Treat a Strident Lisp

STRIDENT LISP: And if my student is demonstrating a strident lisp? “Oops, just a little too much air. Can you try it again, but be a little more gentle? Like… this?” or say something like, “Oops, that ‘s’ sounded a little too sharp. Can you use softer air this time?”

My favorite tools for correcting a lisp

There are certain tools I find incredibly useful when trying to correct a frontal lisp or a lateral lisp.

As I mentioned earlier, one of my main objectives is to establish the correct lingual resting posture. To do this, your student really needs to understand the “basics”- including where “home” (aka the alveolar ridge) is located.

My suggestion is to have a typodont on hand.

This allows you to simply point to a model, so your student can easily visualize where to place the front part of the tongue while at rest.

An additional item you’ll want to have on hand is a mirror. Ideally, you would want something small with a stand that can be positioned on your desk. This would allow your student to easily move it while trying to focus on lingual movement and positioning.

Finally, you’ll absolutely want to check out my Correct that Lisp resource on TpT!

This is a clear, step-by-step program that will provide guidance for you as you treat lateral lisps or interdental lisps.

FAQs About Lisps in Speech Therapy

What Does a Lisp Sound Like?

This can depend on the type of lisp! It might sound like “TH” for “S” (a child says “thun” when they mean to say “sun”). It could also sound slushy- like saying “SHUN” for “sun”.

What Are The Main Types of Lisps?

The main types of lisps include interdental lisps, addental or dentalized lisps, palatal lisps, lateral lisps, and strident lisps.

When Should a Child Receive Speech Therapy For a Lisp?

This can depend on many factors. Some lisps, such as interdental lisps, are considered developmental in young children (4 and under) and may resolve without treatment. Other lisps, such as lateral lisps, are not considered to be developmental and require specialized speech therapy services.

Factors to be considered include the age of the child, the severity of the lisp, and its impact on intelligibility, participation, and confidence.

This is my clinical perspective as a school-based SLP, and it is not legal advice. It is important to note that school eligibility varies by state, district, and educational impact criteria. School eligibility decisions should always be made by the student’s team according to federal, state, and local district guidelines.

Can an overbite, tongue thrust, or mouth structure affect lisp treatment?

Yes, factors such as an overbite, tongue thrust, or mouth structure can impact lisp treatment. This may vary on a case-by-case basis. A tongue thrust, for example, can impact the tongue’s normal resting posture. An SLP may still address the speech sound error, but if the structure or oral resting posture appears to be impacting progress, then the SLP may consult with the appropriate provider (i.e. dentist, orthodontist, orofacial myologist, etc.) This is my clinical perspective as a school-based SLP, and it is not legal or medical advice.

About the Author

Karen Krogg, M.S., CCC-SLP is an ASHA-certified Speech-Language Pathologist with over 15 years of experience in preschool, elementary, and middle schools, as well as outpatient pediatric settings. Additionally, she creates effective activities and materials that are trusted by hundreds of school SLPs and are available at her TpT store, The Pedi Speechie. Her most popular resources include her Minimal Pairs Bundle, Semantic Relationships Worksheets, and Lisp and Vocalic R Programs. Her work, including Ideas for 7 Fun and Easy Ways to Get Moving in Sessions and Tips to Teach Core Vocabulary to AAC Users, has been featured in The ASHA Leader. When she isn’t treating speech sound disorders or writing IEPs, she’s reading about medieval history or hanging out with her husband and two children.