I would not take my child to a school that uses corporal punishment. I believe parents should have the right to smack their children (below the neck) when they misbehave, if positive reinforcement is not found to be useful.
I draw the line at letting teachers hit students. For a start, you are not there to supervise this. You need to place a lot of trust in your child's teacher, and hope s/he would not take it too far. Also, there are teachers out there who would use corporal punishment excessively. I wouldn't risk letting my child be in an environment where s/he could get physically punished by someone other than myself.