No I don't believe in spanking, and my experience as a teacher just reinforces that belief, for two reasons.
One is that I think once you've started down that road it's hard to turn around. At school I find the children who I know are spanked at home to be harder to manage (not impossible, just harder). Whereas disapproval, time out, reasoning etc . . . work very well with children who aren't physically disciplined at home, when I use those techniques with kids who are spanked they think "Oooh, she didn't hit me, I got away with it". As a parent I want my child to behave because he understands the values behind my rules, not because he was afraid of the consequences. Children who behave out of fear tend to revert to their old behavior when the adult's back is turned. Children who understand the reasoning/values behind good behavior tend to keep it up.
The second reason why I don't like spanking is that I think it's unneccessary. I'm a special education teacher and I've done a lot of work with emotionally disturbed children. If I can manage a class full of children who start the school year biting, throwing chairs and otherwise completely out of control, and end the year behaving 1000% better, without spanking, I think I can manage my child without it too. I don't believe that spanking causes problems every time, but the research pretty clearly tells us it causes problems sometimes, and I don't see a reason to risk it when there are many ways to handle children that don't carry the same risks.