I've been there ...done that in Baltimore and DC schools...
-Look around to see if there are any classroom rules on the wall...tell them to stick with those and do their work
-Tell them the teacher has a prize for best students
-Tell them the teacher said to call their parents if they act up, and she texted all their numbers to you

. Go into full on Oscar Award winning acting role and pretend you about to call their parents, act like you leaving a message

.....watch them get in line..
- Disturb another teacher to see if they would take the most misbehaved kid
-Also play 20 Questions....... Kids love 20 Questions especially if they never played before

...that will keep them amused for at least 45 mins to an hour if you do it right... gospel
-Just try to hold it down till 2:30 pm ..
Caution..This is only good for K - 6..... I have other "stop acting EXTRA crazy cause I'm a substitute and you think this is vacation" procedures for the older kids..