What a lovely combination of conditions.
If you have a medic you speak to about such things they should be able to offer some more tailored guidance here, as well as observe what you are doing and give corrections and suggestions based upon that. Don't know if you have in school assistance for it but they should also be able to offer something.
If school is boring it does not help, and schools rarely fail to be anything but boring in my experience.
I got around that one by setting some of my own goals. You still get to pass the tests as school but they do have other books and things you can learn off your own back.
If you have not found some interests yet then maybe get a few of those. You can also use them to reward yourself if you can't tie them into a lesson.
Burning off a bit of energy is not a bad plan. Whether you can pedal to school, go for a run/cycle/walk/swim/some kind of gym equipment/something beforehand or during is what you get to figure out. Bonus is exercise is good for a lot more than that.
Eat right. Many theories here but if you want to pack in the sugar cereal in favour of something better (granted most bread in North America also seems to have sugar) then go for it. This would also mean skipping the coffee, tea, fizzy drinks, energy drinks and whatnot at school -- adding stimulants on top of what you might already take is not such a great plan. Go with water if you can manage it, I don't know what Canada has for squash offhand but I did like crystal light when I was stateside last time as a substitute if the water was not something you like by itself.
The elastic band/hairband on the wrist that you stretch and snap yourself with is more of a centring technique but can do things for you if you find your mind wandering.
If you can figure out your distractions then you might work on those (for some this means a clear desk, others I have met with autism go completely the opposite way -- on desks and engineering/fiddling types then "those that are an absolute pigsty and those where nothing happens" is a common quote). Whether music, isolation headphones (or maybe earplugs) or skipping them entirely is a good plan will be on a case by case, not to mention you still have to listen at some point.
Fancy glasses is more for dyslexia but if you wanted to spray some sidewall safety glasses with something dark to cut down peripheral vision you might gain something, in addition to being teased so be aware of that one.
A routine can help, though such things are harder to establish.
As others mentioned concentration is a skill (as is taking exams and depending upon what flavour of autism you have you might be particularly good at a few of those). If you want to try to train your memory then that can be a shortcut to it/come as a happy accident
Also if you have never been taught microexpressions then maybe pick a few of those up and learn to watch for them during classes. That will definitely keep you focused on things. If your autism is the flavour that sees human interactions on the harder to understand side it might end up as a skill you can use rather than innate but still worth knowing
