I have two DS, the oldest is 12. He's clever but to my eyes he is rather coasting at school. His marks are ok - he rarely fails anything, but he's never top of the class either. He does his homework as fast as possible so he can get out with his friends or get online with them. If he gets low marks on something, he's briefly disappointed - but then shrugs it off and gets on with what's next. My worry is always that these low marks / low effort will become the norm, if he's not hauled up on it every time.
During lockdown we had some very heated discussions, with me trying to make him spend longer / think more deeply / learn more thoroughly the work that was being set and him doing (to my eyes) the bare minimum.
I don't know if IABU to put some pressure on him, or not. Some of my friends claim that they leave their children completely alone to get on with school work, they don't supervise or check homework, they say that it's the child's responsibility to get on with it. I have to say that these friends tend to have very well-behaved girls, who generally get top marks, worry about not doing enough homework if anything etc. Other friends are probably OTT: supervising and checking homework, drilling their kids, punishing them if they get poor marks or fail a test.
I don't know what's normal! I was a typical swotty girl, I wanted to please my parents (and they made it very clear just how important this was to them) so I worked hard to get good marks all the way to Uni and beyond. I don't know what to do with a child that doesn't really care when he fails. I should be glad that he is so resilient, and doesn't base his self-worth on pleasing me... but how else do you motivate children?
YABU: leave him to get on with it, if he wants to do well he will put the work in. And you let him live with the consequences.
YANBU: at 12 he's too young to be left to this, and as a parent it's your job to push him on a bit if you think he's slacking, so that he doesn't let himself down.