Poor Schwarzenegger. This brawny, burly man was cast against his type to play a kindergarten teacher for comedy purposes. And the result turned out to be predictably dire. Reitman isn't a very good director, Schwarzenegger isn't funny at all and even the action was pretty bland.
Kimble is a tough and hardened city cop. During an undercover mission, his partner falls ill and he has to take over her part of the deal: go undercover in a small-town school and be on the lookout for the family of a criminal. He isn't really fit to deal with kids, but the mission is important, so he's willing to give it a go.
The comedy is slim, apart from the obvious mismatch there's not much to laugh at. The kids are pretty annoying too, the criminal elements are underdeveloped and the direction is bland. Like most blockbusters, the pacing is decent, but you've got to wonder how this was ever a popular film.