I would not ever tell him to be a good boy again. He is a good boy. You don't like his behavior, and he obviously cannot apply what he knows about good behaivor at school, it is happening into home time because he may be overwhelmed with the school expectaion; and that, in and of itself, is a special need. The question is, why?
He is very young to be in kindergarten. Most kindergarteners are within a year of age 5 and generally, it is best to send children to school on time. That means that very smart kids with late birthdays may wait, and it absolutely means that kids with issues should not wait, they should also go to school on time. When almost all the kids are within the margins of a year of the age 5 cut off date, special needs based on developmental delays are obvious to everyone, as are academic and learning delays as they age.
He is being compaired to kids who have a whole year on him, and, he is probably in class with kids who have two years on him, as kindergarten redshirting is at an all time high and some kids are closer to 7 than 5. That may be your issue.
I am assuming that your son is extreemly bright, and that you had him evaluated by the school prior to enrolling him in Kindergarten at age 4 with such a late fall birthday. Being very smart can create relative weaknesses in areas that are more effected by age, like motor skills, social skills, attention skills, and behavioral expectaions. Some of that is created artificially because of the relative age of the rest of the class, and some is created by the relatively high IQ of one child. They can read well, answer congnative questions well, but they cannot sit for 6 hours, cant' navigate a 7 year olds social manipulations, cannot hold a pencil like a 5, 6 or 7 year old...so, when school turns to these areas of weakness, they get up, run around, and become disruptive, though, in situations where they are accomodated for thier weaknesses, they have more age appropriate skills, and seem to "listen." It would be very common even, for a smart child with a relative weakness to say "I meant to act that way" instead of "I can't make my letters right, and I was supposed to be so smart, and it makes me feel dumb, so I would rather be bad instead..."
All this could be identified in an evalution with a nueropsycholgist. You would also get information that can rule out ADHD, which can cause the very same kinds of outcomes, for very different reasons. The point is, you need to know which one it is. If it is a realative weakness caused by his young age, and he is in class with kids who will be 7 before the year is out, you may want to investigate that as the issue. If the neurosychologist identifies issues with attention (according to the normative standards for his exact age) then you know that you have something specific to intervene with. In any case, if he has been promoted to kindergarten at age 4, a nueropsychological evaluation may be very worthwile, because you need to know how bright he is, and where to supplement his school program, as well as where the relative weakneses are, so that you can help him to learn coping strategies other than getting into trouble "on purpose" to avoid tasks he finds more challenging, which is a very typical presentation for extreemly bright kids.
M.
After reading a couple fo the other answers, I just wated to clarify, I am not suggesting that maturity be the key for school entry. Age is the key for school entry, and age has been manipulated so such a degree is part of the issue here. Children who are old enough to go to kindergarten at the time kindergarten starts, should go to kindergarten even if they are not "mature." That is the real disservice to kids, holding them back, which accomplishes the opposite of what many parents are trying to do by holding them back, it actually causes more school failure than it prevents because children with real needs that would have responded to targeted intervention services are either identifed a whole year late, or worst case scenerio, are always not quite behind enough to qualify before it is too late. The single most preventable correlated event associated with school failure, drop out, illteracy, drug use, and juvinile delinquency is being older than typical age/grade. It may not "feel" like that when children are young, but the data does not lie. That is not to say that some kids will not experience success if they are older than grade, but that is anedotal, and the data does not bear this out for the majority.
Just do not want to have anyone read my response, and pull a child out of kindergarten who is having these same issues who may be fully within the 5 year old cut off, because that would be a mistake. Children who are old enough to be in kindergarten, and who have issues, should have the issue evaluated so that they stay with their age/grade peers, and the child receives targeted intervention services. Holding them back masks issues that may then never be addressed that fester to have life altering concequences. MR