Seven students stand in front of the class. The rest of the students put their heads on their desks. The seven then move about and each touches a student. Once touched, a student sticks his or her thumb up. Then the seven say "heads up seven up!" The students who were touched then get a chance to guess which of the seven touched each of them. If they guessed right, they get to change places and be one of the students in the front.

Here's another version

This one too is played inside a classroom. All the students put their heads down on their desks and extend one thumb. The teacher then secretly chooses one person as "It." This person goes around touching the thumbs of six other people. If a person is touched, he or she goes to the front of the room. When this has been accomplished, "It" yells, "Seven up!" Everyone raises their heads and tries to guess which of the seven people is "It."