Hello, this sounds a bit like my DS. He has ASD, but until he went to school, we had no clue. He didn't have anything that my (admittedly uneducated) eye had ever picked up on as autism. I'm ashamed to say that until I witnessed his ADOS test, I never realised how many autistic traits DS displayed.
Another big eye opener was watching videos about autism on YouTube. I could see a lot of DS's mannerisms in the kids I saw, particularly noises he made, and the extent to which he repeats things I say after I have said them. He has an excellent vocabulary and spoke very early, so i just wasn't looking for problems with his speech.
At school, he would never sit down to join in with the other kids in his class, he would get extremely angry in a flash, be inappropriately direct to adults, could be violent to other kids, and was constantly trying to escape from the classroom. At first, I put it down to him being one of the youngest kids in his year.
If you are worried, an Ed Psych referral is definitely a good idea. At the very least, he or she will make recommendations to the school of how they can help DS in the school setting.
Do you have anything like a Specialist Teacher team in your area? They were very helpful in giving suggestions as to how DS could be supported in school, too. The more reports you have and evidence you can have that your DS is experiencing difficulties, the easier it is to get help, ime.
Sadly, our school journey did not end well. A year later, after a formal diagnosis and getting a full statement, school were still treating DS like a naughty boy and tried to have him sent to a PRU. The Head wanted to permanently exclude him, and promised he would talk to other local heads and make sure no other mainstream school would take him either. After a wrangle with the LA, DS is languishing on home tuition until Sept when he has a place at a special school.
The school we won is amazing, and will be the perfect place for DS, but I know he could have been better supported in mainstream with the right attitude and a little intelligence, so please don't think this will be the route you will need to take if your DS is diagnosed with something similar.
Sorry, this sounds a bit doom and gloom now. I hope I haven't depressed or worried you. My DS is still the same funny, intelligent boy he always was, bit I am very glad we sought a diagnosis and pushed for labels on everything. It served us well when the chips were down!