5 year old suspended from kindergarden

My 5 year old son has been suspended for a week from kindergarten until the school can "figure out what to do with him" they say. To give some background info he comes from what I consider a stable loving two parent nurturing environment. With that being said..he is extremely strong willed and at the age of two started displaying an unwillingness to want to be separated from both his father or myself when dropping him off at daycare. It escalated over a year or so until it resulted in him being kicked out of daycare. He would figure out what he could do that he wasn't supposed to do just to get sent home...I.e...spitting. kicking, hitting.  This con.'d for about three more daycare as it progressivley worsened ultimately resulting in being getting kicked out of them all.  I would say that my son appears to very smart. Compared to others at his level his teachers have commented that he knows things beyond what he should. With that being said...the first week of kindergarden my son was placed on a BIP. The plan has been revised three times in four weeks. My son has run outside of the school to the road on two occasions. The BIP says my son is defiant that he refuses to comply. Intellectually he is above where he should be but that he will not sit still and demands one on one attention. I wrote aetter requesting the school do testing and am awaiting a response but I am lost as to why my son acts this way. Any advice is appreciated.