Has your son been in a "school" environment before??? If not, he is having adjustment problems.
Also: maybe he is not ready....
Some Moms, hold their sons back... as sometimes, boys are not yet 'ready' for school yet. It is a lot more "structure" and yes, following directions and expectations of cooperation... and this is hard if a child is not used to that or not yet mature enough for it yet.
The red/green cards that the previous poster suggests, is something that MANY teachers utilize... and works well. Perhaps use that at home, with your son, too.
Is your son in a private or public school? What is the Teacher/student ratio? MANY times, a Teacher simply cannot attend to a non-compliant/disruptive child... they have 19 other kids to teach too. So, naturally is it not a one-on-one attention. Or, maybe your son is just overwhelmed with all the daily requirements on him... thus he is over-loaded and over-stimulated... perhaps, and his acting out is just his frustration showing and he does not "know how" to express himself otherwise... nor his feelings.
Before just slapping a "punishment" on him, try just talking with him. See what is going on in his mind... and IF he has any idea 'why' he is so disruptive. OR, maybe there are peer issues or Teacher issues. Ask him...
Many times, a kid acts like this because they cannot express themselves, or are not allowed to... or sometimes they act this way because no one will view them otherwise as being "good'" anyway, or they are talked 'at' instead of with.
What sort of specific issues are his problem, anyway? Not listening? Hitting? Loudness? Bullying?
The Teacher should ALSO detail... what HER "discipline" is, in class. AND, the results. Or ask her. YOU are the parent and should be well informed by the Teacher as to what the details are. AND if any other kids/parents are complaining about your son.
But, you said he does not listen to you, either. So you need to get this solved. Cause and effect consequences. If he balks tantrums about it, then fine. At a certain point, if they know a Parent will always give in and is a push-over... then they will never listen. A child needs boundaries and rules, and incentives. Perhaps have him "earn" things.... a nickle in a jar for helpful things he does, and take a nickel away for disruptive things he does.
At this age, what was once "cute" behaviors is now considered "disruptive" problems. The older a child gets, the less is tolerated, especially in school.
All the best,
Susan
Many good suggestions here....