My son has sensory issues that impact his ability in a classroom if we don't work on it. And I agree that a learning disability (even mild) could make him have this reaction. He could perhaps use some better coping strategies with his frustration. My son will be dealing with sensory issues his whole life but we are helping him learn to cope and take care of his own needs with it.
One thing they do with kids like my son is set up a thermometer scenario. His moods and anger are a thermometer. At the bottom, it is green and this is when he feels good and not upset at all. Next is yellow when he starts to feel a little agitated. Then orange when it is for sure a blowout is coming but you still can possibly stop it by recognizing it. Last is RED, and this is full blown meltdown or acting out. The goal is for the child to look for this thermometer themselves and recognize that they have to use their words or do something to stop the colors from changing (especially to red). Until they can do this themselves, an adult in charge looks for when the child's thermometer is changing and brings it to their attention offering them known calming things. (using wordsto express exactly what is going on, activities such as chewing on something hard (straw, gum if allowed), deep breaths and counting to 10, some quick physical activity, having a cool off spot to go where no one will bother him for a couple of minutes until he calms down, etc.) Just using the language of the changing moods and coloring a picture of a thermometer (ball at bottom and then line going straight up with changing colors) helps them understand what is happening. That's the first step to controling anger. Remember that he is as unhappy inside as he looks outside when he has an outburst. He might be dealing with more than you know at this point. Good luck.
Anger issues are a symptom, he may very well have a learning issues......
My son is very sound-sensitive and can get very angry when there is a lot of noise
Get his tested
I'm not so sure you are dealing with an anger management issue. Have you ever considered having your son tested for learning disabilities? Just wondering ....