I think you're good to try and help, but many ppl just want others to tell them quickly and easily, and they don't practice what they think they've learned and by test time, they've forgotten.

Please don't overload yourself trying to help them. They need to learn now to ask the teacher for help, or pay for a tutor, while they are young, or when they are older they will still expect others to help them get by.

Get your grades. Who knows, when you excel and have that great job, you might have an opportunity to hire someone in your class behind you.