Well done!
I get that all the time and my ds has a diagnosis! "Oh, all boys do that" or "its just a phase, they all go through it" - drives me batty.
Friends don't know him as well as you do, trust your gut instincts, I'm a big believer in mums being the experts on their own kids.
Remember, children behave differently in different settings. Some can't cope with school and will display behaviours there that you might never see at home, others might keep a lid on it at school and act up the minute you get them home. They are all different.
Trust yourself to know your son. If you are worried go ahead with the referral, all they will do is take a history, have a chat and maybe either play with or chat to your ds for a few minutes. If they think there's something worth investigating you can take it from there, if not, at least you will have put your mind at rest.
I am not at all impressed by the school's attitude. They have a duty under the SEN Code of Practice to support your child to access the curriculum effectively. If they are the ones raising concerns about his behaviour, they are duty bound to bring in the appropriate professionals.
this is the government's website that sets out how the Special Educational Needs process should be followed. If they aren't doing this, they are in direct contravention of the SEN Code of Practice (SENCOP).
As far as I can tell, he is currently on School Action and has an IEP (see above link). If he still isn't making any progress, despite them trying different strategies on the IEP, then he should be moved up to School Action Plus and an Ed Psych brought in to assess him.
Its the SENCOs job to make sure this process is followed and to bring in the external professionals as appropriate. SENCO means Special Educational Needs Coordinator. Its actually his/her job to coordinate all the external professionals that are involved with children in the school, therefore its her job to bring in the EP.
They can't tell you they have a problem with your son's behaviour in class, but you have to sort it out yourself. His behaviour in an educational setting is their responsibility and the first line would be to bring in an Ed Psych to assess whatever problems he has that could be considered a barrier to his learning. If its something the EP can't diagnose, they can also ask for you to get him referred, but those two things should both be happening, its not an either/or situation.
Sorry, I'll get off me soapbox now.
It just makes me so mad, my ds1 was let down all the way through infants as the school refused to see the problem or bring in outside professionals. He went into freefall when he hit juniors in year 3 and I still ended up calling the EP in myself.
(That's a thought actually, check your local council's website under LEA (Local Education Authority) and see if there's a phone number for the Ed Psychs. If there is, give them a call and talk it through with them. That's what I did and within a week they'd been in to assess ds and give the school a huge boot up the backside.)