Keeping that mental attitude that you can do your best is very important, it would also encourage you to not give up on a problem so fast but rather think and find new ways to solve that problem. Getting continuously cranked out because of school work can be easily done over. All it takes is getting to know what works for you and practice it out using some exam tips.
One way of getting smarter in school is using this school hacks, you can Record the lessons during a lecture, you can basically use your phone recorder to do that since many phones have that, an listen to it later, it would refresh your memory on things you have just learnt, and it is always better to listen to it on the same day you made the recording, this helps you to assimilate it properly since you have just being taught just some time ago. It would keep it fresh in your memory, so the next time you listen to it, you would fully understand that particular lecture. It would all come home.
You can also make it all fun, with this next school hack, decide to reward yourself with a treat or snack after every major study time, or growth. After checking yourself to see how far you have come. You can use a short break to reward yourself with some chocolate or a nice drink. It would help motivate you and inspire you to do more. This helps you also to relax and go for it again. While you read there could a bit of tension to cover a topic or subject but after a break with a rewarding treat, you would feel like you are starting over again with a new freshness and vibe .