If your friend is lacking behind with studies and the school work. As being a friend you shall guide to the right way. You tell him to come home and study with you. If he says no you go to house and say him to have a race for who finishes his/her work before gets a treat out of the other one. This way you will have fun with studies.  
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We can help him by making him understand how important studies are after passsing we can sit  min the facebook for ho urs together but for now he he needs to iunderstand that studies is important