Start with a Money Jar of say $5 and let him know that he has earned this money, and on Friday if there is any left he can go to the store and get anything he can afford with his money, but everytime he hits or pinches he gets $1 or $.50 or something taken out of his jar. When you pick him up from school, if he did not hit or pinch all day, he need immediate praise and gratification by either adding extra money to his jar or giving him a sticker or matchbox car, anything special to him. If he hit or pinched when you pick him up from school. Let him know that you are not happy (calmly of course) with how he behaved today, let him know it was not appropriate and why he shouldn't do the bad behavior and that you are going to have to take money out of his jar. (You can also use stickers on a poster or color a felt board or magnets on the fridge to represent a small weekly prize). So the key is to have daily prizes for each day with no maladaptive behavior, reward weekly for good progress and maybe even a large monthly reward (going to the Museum or inside McDonalds to play or the zoo etc.). As the behaviors become fewer, you can start to take away the daily prizes and just use a lot of praise and pretty soon the behavior has disappeared and you can slowly take away the weekly and monthly prizes.
I use these techniques at my facility for adults with brain injuries. They really do work, all though they do take time. Good Luck.