E.B.
My daughter has been to counselors, therapists, psychologists, psychiatrists, at various times due to her anxiety, depression, and because of her complicated medical diagnoses, so I will share a couple of things that I noticed in your post, (as a parent, of course, not as a professional).
The first thing I noticed is that you said you "tried the approach" of letting the teacher know that that your son refused to do homework. But you didn't say how you approached that, and whether you actually did it. What we have been taught in counseling sessions is that there has to be a clear path and it must be followed. Often, parents set out ridiculous consequences, like saying to the kid that if the kid doesn't come out of the candy aisle in the grocery store that the parent is leaving the store and driving away. The parent isn't going to actually abandon the kid. Or they yell in anger "you're grounded forever". You must give careful thought to your plan, like employee rules at a job (if you violate this safety rule you will be immediately terminated, or you will be reported at once to the supervisor), and you must be clear and you must make sure your child knows that this rule will be followed. Be prepared to follow up on whatever you decide. It can't be an approach, it has to be a clearly laid-out plan.
First, you establish the home rule, at a quiet, calm moment. "Your homework needs to be completed on time, before [supper, bedtime, 5:00 pm, going out to play, watching tv, whatever you establish that works for your family]." You make sure the circumstances in your home work for doing homework (a quiet place, a neat desk, the kitchen table, no loud music or tv to distract, etc). You inform the child of the consequences. "You won't be able to [watch tv, play, etc]. You won't be punished for not being able to do work you don't understand (a young child should not be punished if his handwriting is shaky, or if he really tried to spell "occasion" but spelled it "ocassion", for example), but you will have a punishment if you refuse to try. You will have certain punishments if you refuse to do what is expected of you, you'll lose certain privileges at home, and your teacher will be told that you refuse to cooperate with her". And then once the path is clearly laid out and the child understands, you follow the path. You don't say "I will tell the teacher" and then the next day you say "I promise I'm going to tell your teacher" and this goes on for several days. You say it once, clearly and simply, and then that's that. Let those natural consequences happen. It's helpful sometimes to write out a chart, listing expectations, rules, and the punishment.
And after you're done telling your child the plan and the punishment, if he looks you in the eye and says "I'm not doing it", then you proceed right to the punishment. Remove all video controllers. Password protect the wi-fi. Call the teacher and schedule a meeting. But remain very very calm. Don't appear agitated, sad, angry, or emotional.
Another thing I noticed is that you ask your son why he's angry, ask him to explain his feelings or actions. Now, sometimes, people know precisely why they did what they did, but that's not always the case. Picture a woman who's pregnant, who all of a sudden bursts into tears over nothing, and her partner says "why are you crying?" and the woman just cries harder and says "I don't know" and the partner says "did I do something to upset you" and the woman cries harder, realizing somewhere down inside that the partner was nothing but kind and attentive, but she just is bawling her eyes out for no logical reason. It's hormones, or just a mysterious part of pregnancy.
I write that to say that sometimes, a kid, or a teen, or an adult, struggles with behavior or feelings or responses that they legitimately cannot justify or explain. Asking the child to explain sometimes makes things worse, or makes the child more confused.
A counselor or psychiatrist can help, can provide tools to unlock these behaviors. And I'm not talking about medications. My daughter went through a period of time that was driving my husband and me absolutely bonkers. It was a thing that she was fixated on, that was of no consequences whatsoever. but it enraged her to the point where she would hit and kick and scream and damage things and herself (it was a particular thing in the car which turned off automatically when the engine shut off but she would fly into an uncontrollable rage if whoever was driving didn't turn it off manually). We ended up scheduling a joint session with the counselor, and we all spoke our piece. The counselor gave our daughter some good questions to ask herself, and gave my husband and I some good tools for dealing with this particular situation. Having our daughter be accountable to a third person (the counselor) and having these questions to ask herself when she felt the rage boiling up because the driver let the thing turn off automatically, helped put the whole thing into perspective and she stopped the behavior, after a few sessions.
I want to assure you that even the most loving, attentive, intelligent parents can need a helper when faced with a difficult child. Our first child was healthy, happy, and we faced only the typical new-parent things. Then came our daughter and we questioned everything we had ever known or done. We enlisted help from professionals. Yes, today she takes antidepressant and anti-anxiety meds, but she has not been over-medicated. They are tools in the toolbox that she (and we) need.
I encourage you to get your child to a child psychiatrist. Make it positive. "Honey, sometimes you have trouble with other kids, thinking that they're following you or looking at you, and sometimes it seems that you are having some problems with homework. We're going to talk to a person who can help you feel less stressed." And talk to a professional yourself. Tell that person that you need some tools, some help, being the most effective parent you can be to a child who presents some difficulties. A counselor, therapist, or psychologist won't prescribe medications, and that should not be your first goal. If that person realizes that perhaps a med might help, they will suggest a psychiatrist.
It doesn't mean you're not effective, not loving, not smart, not experienced - it simply means that you have a child who may need a different parenting technique, or some support, or the insight of a professional. And the best parents are the ones who realize that they don't have all the answers, and are willing to enlist someone to come alongside to help if the situation warrants that.