I personally would avoid any preschools that have 3 year olds doing worksheet.
We looked into Montessori schools and I loved one of them but then it shut down last year and SO was never crazy about sending DD to a school that would tap into her strengths.
The nature-based preschool we ended up for DD is wonderful. DD went from not really knowing what to do with herself with a group of peers to being a social butterfly. It still isn't a perfect fit and she is starting to crave more math and writing but those things, we can do at home together.
When you visit the right school, you'd know it. Meanwhile, I'd keep on touring as many schools as possible, even the ones you don't think would work out for your DS just so that you know what you're looking for and also what you do not want in a preschool.
