This could have been a great episode. It had some high points that were classic South Park with Cartman, but it also missed terribly on the Mr. Garrison part of the episode. The Mr. Garrison part had a few good points, but they were very far between.
But the good first. The Cartman part was hilarious. Having Cartman teach the kids was a wonderful thing. As the allusion's section of the episode page says, it references a film (and you could also tag about four or five other films that are similar such as Freedom Writers or even Coach Carter, where some teacher comes in and helps out the underpriveleged kids) and it does it well. I think that it pokes fun at the whole genre by having Cartman do it. It also worked brilliantly how Cartman was able to use the Patriots coach into his whole time teaching with his wonderul way of cheating. That was one of the better references to current events in a little bit on South Park. It takes a pot shot not only at the Patriots, but it also does take a shot at the NFL.
However, for as good as that part was, it really missed on the Mr. Garrison part. It had a moment or two where it was funny. Mainly at the end where Mr. Garrison talks about what determines if someone is a women or not and a few things with Butters. But it missed so much more. The whole chasing down the mouse thing was drawn out considerably longer then it needed to be, and it felt forced the whole time.
Overall this could have been a much better episode if they had focused a little less on Mr. Garrison. That part was too hit or miss to really be considered all that good. But as a whole, it wasn't a terrible episode and was just mainly silly.