Parents who send their children to small private schools sometimes ask me if they should transfer their rising 9th or 10th grader to a large public high school in order to have a better chance getting in to selective colleges. The answer in most cases is NO. Students I work with from small private high schools do as well or better than their public school peers.
Just because a high school is small or private is not a reason to worry about college prospects for students. Statistics on home schooled students show that many of them do better than students who attended public or private schools. There is one exception and that is the quality of the teaching and rigor of the curriculum. The best schools are those that adequately prepare students for college testing and college academic performance.