Everyone needs helps and everyone can help others.
For example.If one day,your classmate is on duty.maybe you could help him to clean up the classroom.You may ask me why i help him?It doesn't have any good ways for me.You are wrong.
When you are on duty,but you have to go home,then what you are going to do?I think you could ask your classmate for help.They may glad to help you.Because you have helped him,so they will help you too.
You help him to clean up the classroom also can make the classroom gets bright and clear.It can makes you and your classmates feel well in the classroom,so you will get good grades.
So you see helping others is helping oursevles!