My son is ADHD, and has started having issues at school?

my 5yr old son has AD HD, he was doing great there for a while, now he is starting to act up in cl ALOT, today i got a call from the school to come and get him, he was yelling at the teacher, hitting tables and knocking chairs over, not listening at recess or pe, i mean the list goes on, i have grounded him from his bike since he loves that, taken tv away, i cant ground him from outside since he is adhd he needs to run and get his ENERGY out, but i dont know why all of a sudden he got worse i thought he was doing better, he dont act like this at home. if he did he would get the wood spoon. what can i do on my part to help him he is in kindergarten, and yes i can handle him, but not when iam not there at the time it happens example school. i have lowered the sugar intake to almost no sugar at all. any ideas would help alot, for things i could maybe do at home to help better his difficulties he's having. oh and he goes to bed at 8pm every night and gets up at 7am for school.thanks for all who answer.