Keeping track of students! Great tool for teaching sorting, understanding of one's place in space and time, number recognition, one-to-one association when you teach each child to recognize his/her number, good grounding activity in the morning, why we go to the office, when we should go to the nurse, the best time to go to the bathroom is at recess...
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Classroom management. This is actually a really cool idea. It would really help during study hall attendance when 6 kids came to you with a note to go to another class! I can coordinate the numbers with my cell phone storage numbers too.