Firstly, I wouldl tell my friend that littering in the class is a kind of bad manner, one should not inherent such habits. I would tell him that our habits shows off over family background. And when we do bad things at school we give out a message that we haven't learn good things at home, so you should not litter in the class. Secondly, I would tell him the importance of keeping our surroundings clean and if he would do that, he may attract many children to be friends.