The term INTELLIGIBILITY refers to the proportion of a speaker's output that a listener can readily understand. This term has nothing to due with intelligence.
If your child is in Kindergarten to Grade Two in the Chenango Forks School District, and you are concerned about a tongue protrusion (lisp) on the /s/ and /z/ sounds, please contact Ms. Shaevel. A program of GUIDED THERAPY is available. See the link for GUIDED THERAPY in the left column of my home page.