OP, I can see why you'd think tech would be great for things like this, but I believe it'll be a bad habit in the long run. If all of your notes are stored electronically, what will you when data is corrupted or when your device breaks? You sure as heck won't spend thousands to recover notes. I reccommend doing it the old fashioned way... with a pen/pencil and a notebook.
I can't see why your notes would be under your bed or in the trash.... unless you're using loose leaf? Try using a ringed notebook, like those college-ruled ones. For one, you can write larger in a notebook than you can with your iPad/S3 device.
You can edit mistakes more easily in a notebook ('precision' erasing).
So it's not quite the answer you wanted to here, but it IS an option. Consider putting your notebooks in your backpack when you are done with them so they don't get lost or end up in the trash. If you're thinking of going to college someday, realize that many professors prohibit the use of laptops in their classrooms. But all of them allow notebooks
I see you worrying about fires, bullies, etc. But be logical here. If you keep thinking worst case scenarios, you'll ALWAYS have an excuse not to do something. Those fires/bullies can also be applied directly to your electronics too, so there's that. Oh, and as another person said, drawing diagrams is much harder on a computer!
Start early, man