At first I thought ez might be a little extream but I'm starting to think that ez is right. Unless you have a court order saying you have to ask for permission from her you can do what you want. I'll read your long post later today when I get more time.
Ok I got to read the whole thing. I remember all this now. Make sure your son stays on his meds and does what the doctors says. It doesn't matter what she tells the school. Your son needs to make an appointment with the school princeple and take a copy of the court orders for the school to keep. Explain it to the princeple and ask to see your daughters file. She may have missdirected the school in writing (good stuff to have in court). You do not have to ask her what and were you are going during his visitations. EZ is right you need to start documenting everything.