Why do japanese students take off their shoes in school?

This week I thought it would be interesting to read and talk about some unique customs in Japanese schools. Specifically, I really enjoyed reading about how they encourage students to see the school as a shared space, and therefore they all do their part to keep it clean.

I know we have some people with experience in Japan, so hopefully they can add some extra perspective.

http://www.ehow.com/about_6127367_do-students-shoes-off-school_.html?dmsp=manual