1. Go to the board when teacher isn't around, clear your throat in loud manner and say "So class I'm about to teach you how to convert 02 into C02 and help trees."
If someone says ANYTHING. Say "It's mean breathing, people breathing."
2. Go to the board bring everyone attention then pick up the chalk/marker and write 2+2=5. If someone ( doesn't say anything ask them what is 2+2 ) or someone says that it's wrong. Say "It is made from mistake just like you were".
Hope you like it !!