Day student admissions can be tougher but definitely not impossible. As with boarding applications it can be a bit of a luck thing in terms of having whatever intangible quality that appeals to the admissions committee that particular cycle. Casting a wider net will really improve the odds of ending up with at least a few yeses. Having lower SSAT scores isn’t ideal but it’s probably the best weak point to have. Grades, recommendations, essays, interviews, and ECs all tend to be more impactful. One nice thing about being local is you aren’t limited to one or two brief visits. Don’t be afraid to ask about attending some sporting events or upcoming plays/music performances. It will help demonstrate interest but also can give you & your son more info on school culture.
I definitely second the recommendation to look at George School. Solebury is another to check out; I’ve heard great things about their ability to provide learning services at a variety of levels. I don’t think of them as a big competitor athletics-wise so it will depend on how important that aspect is to your son, but very much worth looking at.