I am going to agree that meditation should have a more positive effect on the erring student than detention. While detention is definitely viewed as punishment, meditation can be looked at as a strategy that enables the child to reflect upon what he has done wrong to try to figure out why he did it and how he can avoid repeating the offense going forward.
Yes, alternatives to traditional forms of punishment are more effective than traditional ones. Punishment in general, and in schools in particular, should focus on rehabilitation instead of revenge or a need to cause pain and distress. Meditation has been proven to provide many psychological benefits, and will be very valuable in schools.
If you are going to keep a child after school for doing something wrong, you might as well teach them something new and improve themselves somehow. Most of the time, schoolwork is what got them into the situation so more work isn't really going to help. Meditation may help calm them and turn their attitude.
Kids know that meditation is not real punishment. It's a place to go when the kids don't want to go to class. The kids just say that it's okay and that it's better, and then gullible administrators go along with it. Throughout the history of time, punishment is the only thing that works to control behavior.