This is a skills laboratory that goes over how combustion works and how it consumes oxygen. I have used this in late elementary, but only with the teacher performing the task. In middle school ages and up I have let students perform it in groups, but with the instructor lighting the candle.
This laboratory includes a listing of what materials you will need, what the procedure is, and what safety precautions should be taken. It also includes a work page for students to record their findings. Feedback is always appreciated.