Students held fundraisers to make $130 to buy the pole and the flag.
A parent poured the concrete to put it up.
Thursday morning, it was gone
"When I saw it, I tried to turn around and head them back into the classroom, and one of the kids saw it and said, 'They stole our flagpole, how could they do that to us?'" said assistant teacher Mari Huscher.
Police suspect the thieves will try to sell the flagpole as scrap metal.
The students are launching another fundraiser to buy a new one.