Put off . . . filthy communication out of your mouth.
One of the things that is so easy to get caught up in at school is dirty, vulgar talk. As a Christian, you can be a real witness to those who are not saved or to other Christians who have slipped into this mode of speech by never letting any foul or filthy words escape your lips. Ask the Lord to help you to speak well of Christ and of others and to not talk dirty like others do.