My answer will be for the U.S.
You can request a Functional Behavioral Assessment (FBA). This can be the basis for a Positive Behavior Intervention Plan (PBIP). Here is something to give you an idea how it's done.
The idea behind these is to shift from reacting to the student and his misbehavior, to planning and implementing changes in the environment. Hopefully your district has a behavioral specialist who can support the teacher in finding more positive ways of dealing with these challenges.
The FBA can identify environmental triggers for disruptive behavior, such as feeling hungry, sensory overload, getting overexcited from recess or P.E., sitting still too long, etc.
I'm glad to hear that the teacher is reaching out to involve you. It can be helpful to do some brainstorming on your own, and then with your child, and jot down ideas about what might make school easier for him to handle. Here are some things that helped, or would have helped my son at that age:
Provide something to sit on other than the carpet (the occupational therapist can help with this)
Take a break every 40 minutes or so. Get some extra physical exercise. (The assistant in my son's kindergarten class would take my son and another little jumping bean down to the gym to do some extra running around.)
Provide more interesting classwork.
Provide more hands-on activities.
Offer the child the opportunity to choose between meaningful alternatives.
Choose a primary goal for your son to work on.
Create a cozy, inviting corner in the classroom that your child can visit on his own initiative, voluntarily, if he wants to rest and get more inwardly focused.
Create a signal to remind the child about a certain behavior, so as to avoid using the child's name in a negative tone.
Provide some non-verbal ways to participate in group discussions. Group discussions and lengthy teacher explanations can be really hard to handle when you're five and you're energetic.
Provide some special responsibilities, for example set up and distribute snack.
It can be very difficult for an over-participator not to inadvertently obstruct an outside presenter's work. But if we ask the presenter to arrive early and get to know the over-participator before beginning the presentation, it might be possible for the presenter to incorporate the over-participator in the presentation.
You might find it helpful to observe your child in school for a chunk of time. It's best to make an appointment to do this.
If you have time, you might even want to volunteer in the classroom from time to time, to get more of a feel for the dynamics.
Another idea, if there's another place your child could be safely cared for, would be to reduce your child's school schedule, on a temporary basis.
Once a child and a teacher get into a negative way of interacting with each other, things can get ingrained, and it can be hard to turn things around. We found that it was very positive for the behavior specialist to get involved, because the teacher was more open to ideas coming from her colleague than from the parent.
In my son's case, what turned things around in kindergarten was to collect some donated board games to keep in the classroom.
Your child needs to be positively engaged in school, and the school needs to adjust the environment so that he's not so often a square peg that they're trying to make fit into a round hole. Do you see why an observation can be so helpful? You know your child well. An observation can help you identify the ways the classroom environment is problematic for him.
Note about the process of the FBA. (By the way, this isn't "educational testing" in the way intelligence testing or achievement testing or evaluating for ADHD or anything like that; however, the parent would need to sign consent.) It's basically a matter of the classroom teacher, the P.E. teacher, the music teacher, the school librarian, the cafeteria supervisor, etc., all noting down any problem behaviors that may have been observed, and at what times of day and in what situations the problems occur more frequently, so that patterns can be teased out. A school psychologist would make one or more observations.
Some states in the U.S. mandate that an FBA be done whenever a student's behavior interferes with his own learning or that of others; other states call for it to be considered.
