M.B.
This is an excellent question and really something worth considering. The research shows that the single sex education for girls is much better for them as the teaching of things like math and science considers that girls think and learn differently than boys. And, teachers typically teach to the boys and of course, there is the bias that girls are not as good in those subjects. I'm an engineer and even in universities classes there was a bias.
It is way too late in general for Ursuline or Hockaday. However, depending upon your daughter, they may be able to consider her application. These schools are very expensive (as much or more than some colleges), however, in my experience the investment is well worth it. My two sons have been in private all boys schools since Grade 1 (first at St. Mark's of Texas and now at Cistercian). My older son got one of the top 3 scores in his class on the PSAT (and this is a school where 3 boys out of the 40+ get perfect/near perfect SATs) - this is due to the challenging curriculum. I would not let the cost discourage you as many of these schools offer need based financial aid (full to partial). From folks I've talked to, it's around 15% of the kids qualify.
If I had a daughter, I would choose Ursuline over Hockaday for the same reason that I moved my sons from St. Mark's to Cistercian. There is just plain ole too much money and too little parent involvement/supervision for a subset of the kids at Hockaday and St. Mark's. This impacts the other kids in a several negative ways in my experience and I've heard it's worse at Hockaday for the girls than it is for boys - the clicks are extreme and the access to drugs/alcohol is just too easy. This is partly because some of these parents don't feel the need to get to know other parents (because they're not part of their social set) and they don't really care who their kids spend time with or whether their kids are supervised when they're with other kids. This leads to dangerous behaviors IMHO. I know families that live within a few blocks of St. Mark's that still send their sons to Cistercian for the same reason.
