Addendum to prev. rant:

And now my boss can't cope with the fact that I need to attend job college twice a week for two days, LIKE EVERY OTHER APPRENTICE HE EVER HAD, and decided to scrap my colleague's and my downtime project under the pretense: "There is no downtime" and "If you're only here three days a week, we gotta scrap it for time reasons".

Piece of horseshit.
How can you be so stupid and not know that in beforehand?! Every other apprentice you ever had, had the same job college plan.

If this behaviour isn't getting better, I'm out after my apprenticeship ends.

You could tell him that every apprentice it had as well and that it feels like a punishment what's now going on because it's important for you. That's a normal thing to say. We're all human, as employee we do what we're told, but it's more comfortable to ventilate our opinion. You have to give your boss the chance to review his pov by giving input. Especially if it's a thing that will makes you leave after apprenticeship (won't say that tho, that could lead to immediate exit, legal or not, broken relationship can be valid for termination, world is less nice than we think).

But express how you feel about that stuff, it's important. And you'll see it DOES matter.