http://www.mamapedia.com/questions/4017124414855512065
Here's a link to my exact same question. They all gave some good advice there as well.
I can give you good news: just when you think you're about to take up alcoholism as a hobby, he will turn around and be the kid you always knew you had.
Remain consistant. I found that when his teachers at day care gave him a choice to participate or to roll around on the floor/be disruptive and gave him consequences to his choices, it was like night and day. but I'm lucky in that the day care and I stayed on constant contact so that we didn't become complacent.
I have talked to my ped. and she says it's a phase if there is no other underlying issue. I'd also consider making sure he's not hypoglycemic. I found that when he ate smaller meals (he eats breakfast, then a yogurt or babana then lunch and then another snack and then a snack when he gets up) throughout the day, he seemed to focus better. Might wanna try that. My Dr told me that it is plausible that he was going too long without eating therefore dropping his bloodsugar and then voila...rambunctious kid.
Good luck to you. I been there. I'm sending good thoughts your way.