Is it the same teacher/s every time? Or in the same subjects that maybe aren't his strong subjects?
As pp said teachers too are only human, my dd struggled last years at school, mainly due to one particular teacher. I backed the teacher while also supporting dd and not obviously knowing the truth as I wasn't there - then the teacher let rip at me one time! Before I'd even said anything! I'd gone through the switchboard and got put through to her, as soon as she knew who she was speaking to (literally 'hi, it's graphista dds mum') I wasn't even calling about the problems, there hadn't been a recent occurrence, I was calling because there was a school trip coming up and I needed to check something.
Completely lost it! In the midst of this she used certain mispronunciation of words and odd turns of phrase that dd had described to me before (and which she'd never said to me in many conversations before) - long story short I learned this teacher had basically fooled me into thinking she was behaving reasonably AND that dd wasn't the first to have problems with her.
Not saying dd was perfect in her reactions either - just saying it may not all be dss's 'fault'
I also have lots of friends and family who teach inc one who works in a behavioural unit that's basically a school for kids nobody else will take - and even she says some of the time these kids have lost their trust in teachers due to a bad one early on, think all teachers are the same and it spirals from there.
Even with all that in mind I said to dd about picking your battles, not giving someone who maybe does have something against you more ammo etc (let's face it we've all met adult bullies and know the more reasonable you are the less you're playing into their hands of painting you as the bad guy).
Not saying give him ideas either - but to keep in mind just because it's a teacher doesn't mean the problem isn't 6 of one and half a dozen the other!
"he lives by the rules and rarely causes arguments at home, but school is another story!" Another reason I wouldn't take it as read that it's all him - it's out of character. Although another possibility is peer pressure
Teachers shouldn't NEED to be shouting, are they shouting just at him or to the class in general? I wonder if they're newly promoted and trying to prove they deserve it?
Also all stick and no carrot doesn't work for behaviour modification in anyone let alone teens. Rewards can take longer to show results but have longer lasting results too.