One of the most effective way to model moon phases in a classroom is to use "Moonpops". As the students turn in a circle they can observe the moon phases on the lollipop-like sphere, which is half white and half black. A spot on one wall is designated the sun, the student is the earth and the "pop" is the moon. As the student turns in a circle, keeping the "lit" part of the pop towards the sun, it's easy to see the changing moon phases. Students then created Moon Journals in which they will record their observations for a complete cycle.