Protractors are for measuring angles, not frisbee catch. Read the two variations of teacher statements below, noting how the second utterance is a much nicer way to gain compliance. No, you can't paint without an apron. I know you feel uncomfortable in an apron, but it keeps paint from ruining your nice clothes. I'm glad you noticed my new plant.
Plants are for looking at.
Touching the leaves can hurt them. Nowadays, we don't like it when someone is lecturing or nagging us. We didn't like it when we were students either. We felt as if the speakers were condescending toward us, and often ignored those people or rebelled against them. Keep it short and simple.