When a child mumbles

Here is a current dilemma. I have a teacher who swears that 2 of her students can't talk. They sounds like they have "marbles" in their mouths (or so she claims). I went through the entire procedure of getting permission to test, testing, and re-testing. But neither of these students actually have trouble with any of their sounds. In conversation one of the students does not close his lips and speaks very rapidly. I can understand why that would be difficult to understand. The other student does not have very good English skills. Although her mother and the interpreter said she is somewhat hard to understand, no one can say specifically why.

So are these children who qualify for speech therapy? A child should be 100% understood by age 5. If they are not understood well at age 7 does that make them eligible?