DOES YOUR CHILD HAVE A LISP?
Some children produce /s/ with their tongue between their teeth when they are first learning; however, to correctly produce this sound their tongue should be entirely behind their front teeth. If they are 3-years-old they should begin to produce /s,z/ in conversation but may not yet be 100% accurate. If your child is 4-years-old, it is expected that they be producing /s/ and /z/ correctly (tongue behind their teeth). If they are producing /s,z/ with their tongue between their teeth, here are some activities to try.
1. Explicitly model /s,z/ using a mirror. Show them that your teeth are fully closed and make a big smile.
2. Instead of directly associating /s,z/ sounds with letters, use different names to dissociate from their current production of the sound (for the time being). I use the "snake sound" for /s/ and the "buzzing bee sound" for /z/.
3. Have your child "show you all their teeth" or "make a big smile." Then ask them to make the "snake sound" or the "buzzing sound" by copying you. Again, you can use a mirror to help them see what they are doing and catch themselves when their tongue sneaks out.