Flags Not Part of Geography Class

In Jefferson County, Colorado, seventh grade geography teacher was placed on leave for placing flags of other countries in his classroom. First year teacher Eric Hamlin displays the flags of different countries as part of his World History curriculum, rotating them out based on the countries being studied.
This apparently violates a new statute in colorado, which states:
"Any person who displays any flag other than the flag of the United States of America or the state of Colorado or any of its subdivisions, agencies or institutions upon any state, county, municipal or other public building or adjacent grounds within this state commits a class 1 petty offense."
What are these people so afraid of? It's this sort of statute that gives us presidents who ask, "Is our children learning?"