Kid's differences

My both kids having their summer class. Actually they don't need it because since first year they all passed their subjects . (Thanks God!) They don't have failure grades but my son's grade for the last semester is depressing. He got only passing grades 3.0. My gush!!! he is soo lazy to study despite of my advices. I hope he will change because he will be third year engeneering by June 2009. My son is more talented and intelligent than my daughter but my daughter has a higher grades because she study more in the house. They have the same course Engeneering and same school . So many times , my daughter review and study untill 0ne o clock AM during examination day but my son just pip her notes for only 30 minutes then sleep.