Over the years, I had to take classes for my teacher certification and I attended quite a few in Madrid. I really had some bad experiences.I eventually just signed in and left or found other students who felt the same and we took turns signing in for each other! Instead I explored Madrid and the surrounding areas-much more useful to me!
The only positive experience I had in a language school is called Sampere,started by a couple in the '50s and now directed by their son.Small classes,great locations (near the Retiro) -not only in Madrid -and young/enthusiatic teachers.There are also planned activities during the week. Very reasonably priced.
If anyone has a question about a specific school,feel free to ask me!http://www.sampere.es/