If you feel that emotional intensity is the problem (rather than lack of maturity-- which IS a possibility you should consider, since it sounds as though he's been somewhat sheltered socially and may simply not have had much opportunity to develop that particular set of social skills if the adults in his life have been catering to him), then it would be a good idea to begin to hand over some control to HIM. That is, figure out some ways that he can self-sooth/talk himself down when he's overstimulated. Then let him practice those things regularly, and resist the urge to intervene too quickly.
If your gut tells you that neither of those things "fits" perfectly, then there may be more going on than is within the scope of a parent to handle. Was this a public kindergarten? If so, then there is something fishy about asking a child to LEAVE after less than two weeks.
Either there is something they aren't telling you, or they are probably not somewhere that you wanted your child to start with. Come to think of it, that might be true for a private kindergarten, too.
