School districts — with their fleets of gas-guzzling yellow buses — are watching nervously as gas prices keep rising.

Although most districts sign contracts for gas in advance at a set price, there are often clauses in the fine print, calling for extra payments if the cost reaches a certain price, says KARE-11 news.

So districts like Anoka-Hennepin are expecting to go over-budget on transportation costs at a time when their budgets are already under strain.

"I think for the next three months it's going to be pretty steep, I think it's going to be in the four hundred thousand dollar range of over budget from what we anticipated," Anoka-Hennepin Schools Director of Transportation's Keith Paulson told the station.

And looking ahead, districts may have to alter their bus routes, maybe increasing the distance that students have to walk.

Last time gas prices soared, Anoka-Hennepin made adjustments:

"We increased the walking distance from a house to the bus stop for elementary students we had them walk an extra 44 feet on average and for secondary students another 94 feet for a bus stop," said Paulson. And new routes completely eliminated some stops and helped to streamline the busing system.

Another possible option for districts to deal with the added gas costs, said the story: four-day school weeks.