So how big should the squares be? I've gotten that question from a number of teachers and playground designers about Hopscotch and Four Square.
The answer is that there is no 'right' answer, they can be as big or small as you want. BUT, here are some suggestions to make life a bit easier:
For both these games the key is the size of the kids playing. If you are a kindergarten class, you need smaller squares than a 4th-6th grade elementary logically.
Hopscotch: I recommend about 18" to 24" per square
Four Square: 6-8 feet per square
But the best way is to simply test it out by using some chalk and playing a few games. This would be an excellent exercise for a few students. Put a small group in charge of deciding how big the squares should be for the whole rest of the school for years to come! A piece of chalk, a ruler, and a ball is all they would need for equipment.