The fact that after your meeting with him an explaining your sons needs he picked the one teacher out of five that didn't meet your criteria is not so good.
I wouldn't necessarily discount the possibility that this new teacher is, indeed, a good fit. It's possible that out of all 5 teachers, she/he *is* the teacher the principal sincerely believes will be most patient with your ds and understanding of his unique needs.
You really can't gauge things like patience with young children, or innate ability to relate to young children, or kindness and willingness to meet students where they are at and challenge them to go further by looking at a resume post on LinkedIn - you have to get to know the teacher in person, and you're going to have to most likely experience her in the classroom. Other than having parental anecdotes re experiences with the other teachers who are at the school, do you really have more info to know which of the other teachers would work well for your ds? Aren't you, for the most part, in the same situation with each teacher? This one just might seem a little more scarier or problematic because she's new to the school.
Best wishes,
polarbear
