Alot of efforts can be made to get better grades.
-You said don't say anything like study but I think this should be said. Studying is so important, but most people fail to do it with how boring it is. Studying doesn't always have to be lame. You can use a technique called the Pomodoro Technique where you work 25 minutes then rest for 5, which increases productivity. You can reward yourself a snack in that five minutes, but the sole purpose is to get some serious studying done.
-If you are confused about a material, don't be afraid to ask for help! teachers want you to succeed, not fail, and asking them about a topic or clarification can do alot. Tutors can always help too, provided your school provides them for you. (easy access)
-Put your phone down. The phone is such an annoying distractor to me nowadays, sometimes I want to chuck it in the ocean. There are focusing apps available in the app store that you can download to increase productivity and stop checking social medias every two minutes.
-Study with a friend! A friend can help you stay on track, especially if you two want to be comfortable to study together. Studying together might bring the fun out.
-Ask a teacher for a problem that you got wrong on a test. Never too late for clarification! Being verbal to your teachers is so important because you are there for a reason...so speak up!
-Makeshift tests. If you don't understand a concept or are iffy about it, search questions online and see if you can answer similar ones! If you treat this as a test, you know what material to work on and can even expand your knowledge.