How to lock in?

So, I'm a 11rh grader and my 11th was decent till like September. Then our all three teachers changed and my 11th got fucked, I had to rely on yt lectures to even understand the concept and this took a lot of time. For context, I go to a 8 to 5 school and almost 12 hours of my day get wasted there. The problem is not even that. After arriving home, I be sleepy as fuck that I can't even study. I can't remember the last time I have seriously sat and studied tbh. So yea, any tips on how do I avoid my sleepiness and study atleast 4 hrs a day ? Any help would be greatly appreciated. Thank you!