I've actually heard negative things about Scollars in Collars and I was in class at McCanns with several people who had been to Scollars in Collars first - because Scollars in Collars is cheaper then McCanns.
I can't say enough good about McCanns. They're great. In the class there is a main teacher and then a teacher for every 4-5 people so you get alot of one on one attention.
McCanns is my suggestion
They have a pretty good website you should check out :
http://www.mccanndogs.com/intro.htm