He was kept in a "boarding school" but really it was a place where they experimented on students. Thad had powers where he would get angry and lights would explode. He could communicate telepathically with this girl pretending to be a boy.
There are many books in the series, and they are very long. They have black covers. I don't think they were ever very popular. I read them as a junior or senior in high school in 2014/2015. I believe the books are from a local author around Rochester or Albany.