I think you are new to anime, so I'd recommend...
Your lie in April
Romance, Music and Drama ^
OnePunch Man
Action ^
Rainbow
I don't even know how to summarize this, with a genre, it's just good.
Grand Blue Dreaming
Comedy^
Akame ga Kill
Action^
If you want more animes recommended just message me.
I am not 100% certain on what to recommend, assuming it just need to be a Action x School theme involved in it. Also, the animes I am recommending aren't the types that I would want to rewatch, some are pretty meh, others are alright, some good. But if you are after the Action x School theme then these hit the mark, somewhat.
The Asterisk War
The Asterisk War 2
Not a big fan, but it's good, it also in all honestly has good action in it, with a distinct school vibe.
Sky Wizards Academy
One of the more worse animes I've watched but hey, it got that action x school theme. So check it out yourself, it follows that lane pretty well.
Wise Mans Grandchild
Well... This is one of those where I absolutely loved the everything except the ending, follows the school path well, action is well... In the more lacking, but it's there! Just not as much.
Blue Exorcist
Blue Exorcist Kyoto Saga
Ye... I don't love it, it's alright. Has action, in a school environment though, it's alright.
It depends how much free time you have. I often don't have much free time as I have other activities after school. So one thing that has always worked for me is actually listening during the lectures. I don't know how other countries or schools has it but... Here many students don't pay much attention, leading them to studying way more than that's necessary.
Taking notes, listening in class and asking questions = less studying outside of school. At least for me, everyone is different.
I also recommend going to those extra help/study lectures, our school has those during certain days and hours and I often try to go to them as much as possible, often with a friend. But if you don't have that then I always recommend libraries, there is always that one library that offers study sessions, with actual teachers.
And it's like, free tutoring, which can actually be good. Because the difference between those teachers in the libraries, and the teachers in schools is that one of those two is doing it voluntarily, meanwhile one is getting paid. I am not saying all teachers in schools are bad but, from my experience, if you do something out of your own free will, you actually care for that, teachers in schools may care as well, but again, it's rare they care as much as those teachers that do it voluntarily.
And hey, not all do it voluntarily, some do get money out of it, but where I am from, most do it voluntarily.
Sitting around the right people is also something to think about, not everyone takes lessons serious and it shows in the classrooms, sitting around those people who talk and giggle every 5 minutes isn't good for you if your trying to listen to the teacher. In most cases, the teacher is only mentioning things once, missing out on that information can mean a lot in the long run.
And well, these are just examples on how to study less, but still perform. But if you are honestly in such a deep hole that your on the brink of failing, work hard. Hard work pays off, let's just hope all the hard work you MIGHT put in from here on out, isn't put in to late :)
Good luck, I hope it all works out for you <3
Best & Worst Anime...
Best: Attack on Titan Final Season Part 2
Worst: Sasaki and Miyano
Biggest Surprise & Biggest Disappointment...
Suprise: Police in a Pod
Disappointment: My DressUp Darling