If this is the problem then you should ask him/her for making a time table and then you should also tell him/her to systematically however take notes from his/her friends and then complete his/her homework properly at home or whenever he/she is free. let him/her not to quit the sports because that is not good for the physical development,and restrict her from free and spare time . I hope it helps, pleasse mark my answer as the best answer.
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