Just keep taking it away and not letting him. Eventually he'll get the idea.
Granted my dd is only 5 (will be six in about a month) We've fought this fight since she started preschool at age 3. That first year it took a while, but she finally stopped. Then she started "sneaking' Them into her pockets or book bag. We started having to go through her bag every day. It just wasn't an option, she wasn't allowed to take toys to school.
Lately, she's been sneaking toys into her book bag because she doesn't want her little sister to play with them while she's at school. so we are back to going through her things and reminding her she cannot do it. Sometimes it's a pretty big fight, but as long as you are 100% consistent, he will eventually get the idea. Maybe you can have a place where he puts the toys he's wanting to take with him so they are in the same spot when he gets home?
at 2:36 PM on Feb. 2, 2010