Preschoolers need variety to keep them stimulated. Taking them to the playground to play games breaks up the monotonous scene of the classroom. Playground games can be played with props that your school already has available or without props. Tag, Monkey in the Middle and Duck, Duck Goose are games that involve running, tossing and chasing. The physical activity and competition make it entertaining for young children.
The Internet provides a variety of websites that offer free games. Look for games that are geared toward preschool age children and that have an educational component. For instance, Aven's Corner has a shape train game where preschoolers have to match shapes. Shape identification is a basic math concept that becomes useful later on. Kaboose is another website that offers preschool games for free.
Turn old file folders into game boards where preschoolers have to count or match drawn objects or stickers on the file folder. Since you are creating the file folders yourself, tailor them to your classroom theme. For instance, if you have an underwater theme or lesson for your students, you can have them count the fish on a file folder game board. Another idea is to draw multiple fish and one octopus, and ask kids to circle the animal that does not belong with the others.
Using a large rubber ball, you can create indoor or outdoor games that are tied to an academic lesson. One idea is to have your preschoolers stand in a circle in the classroom. Bounce the ball to one of the students and say One as the ball bounces. The student then has to bounce the ball to someone else in the circle and say Two. This is a basic math counting game. You can also play this game with the letters of the alphabet. If you don't want students to bounce balls inside the classroom, sit them down in the circle and they can roll the ball to one another.