In high school, most teachers teach five classes. Sometimes they're all the same class. Sometimes there are two. Sometimes there are more. We call each different class a
prep, since you have to prepare for it.
Most teachers I know think two preps are OK, and three or more are less than desirable. But many teachers, including me, get three preps over and over.
Because I volunteer to teach beginners, which takes two periods, I have to prepare those, and then I get at least one more to round off my schedule. But most teachers don't have double-period class, and many of them get three preps anyway.
A friend of mine taught social studies at Outahand High School in Brooklyn, where three preps were like mother's milk. Someone asked why teachers couldn't get only two preps.
"It's impossible," said the supervisor. "No one could do that. If any of you want to take it home and try, be my guest."
Now Mr. Geek, who loved computers, decided to take him up on that offer. The next day, he came back with a schedule that gave everyone two preps. Everyone was happy.
Except the supervisor, who got very angry, and then tore the revised schedule to shreds and tossed it into the trash. "You can't just go around making any schedule changes you like!" he bellowed.
Mr. Geek got four preps, and no one messed with department programming again.