From my experience high-school was practically non-school. Yeah you learned stuff but it required very little out of class work. Unless you have a job or some other extracurriculars it seems like you'd have time for both. Study for your finals and study chess.
If you have to chose one or the other it seems like school would be the correct choice right? Although like another poster mentioned, all it may take is a different attitude. Play for fun (you were looking forward to it for so long right?). It was an activity you enjoyed with friends, so you can play anyway without setting your goal on winning the tournament. (Again, if you're too competitive for that, I'd choose school, you have the rest of your life to play chess whenever you want :)
During August and September of this year i was preparing for a chess tournament that is held once in 6 months in my high school. It was supposed to start at the beginning of October and i was really excited, cause i was the 2. seeded player in my school. Then the bad things started happening, i got really sick and the tournament was canceled cause on of the teachers died of a heart attack. Then when everything was getting back to normal and i got healthy again the tournament was canceled cause it was the time in which all the professors were giving grades, test and a lot of homework. Sadly during this time i could barely get any free time to relax and yea i didn't use it to play chess i did it to go out with my friends. On the 30th of October the time of tests and tons of homework had passed the tournament startet and in the second round i (as the 2. seed) played agains the person which i played last time, but in the finals, he was the #1 seed in the tournament. I played a couple of moves and it was pretty equal, the game just started but i was just so mad, cause it wasn't a round robin tournament, if you lose, you are out. And after 10 moves i think, my nerves snaped and i just resigned and went home. Out of the top 10 players in my school 8 of them were in my part of the draw. Now i don't know what to do, there is a tournament again, in March or April but idk if i should play cause i need to start studying for my finals cause i am a senior and this time next year i will be in college. I have never had luck with the draw but it is just stupid for the top 2 players to play in the second round. So i am asking for your advice, should i play in the next tournament or should i focus on school more? I really want to win the tournament and leave school as the champ but idk if i can balance it and i think if i play i will have really tough opponents to play...So what do you think, to play and to try to be the best or just focus on school and ignore the tournament?