I am very sorry that you are perplexed in a difficult situation. I guess you are an intelligent and sharp student of your school therefore your so-called friends are demanding or blackmailing you. However it is now your duty to rectify your friends' attitude. Tell them if they would rely on your efforts and hardworking and not work hard themselves, they might pass the exams and promote to next class, they would not be able to justify the standard of the new class and the advance concepts. Insha Allah they will change their behaviour and be grateful to you and if they don't do so, it means they are not your sincere friends and you had better make other friends who may be sincere to you in future.