Students leave the bus on the first full day of school in Florida last August. (AP Photo/The Florida Times-Union, Bob Mack)

The 1,500 yellow buses run by Fairfax County, Va., public schools drink plenty of gas, nearly $12 million worth a year. But falling gas prices are expected to save the district $2.8 million – funds it plans to spend instead on instructional programs and teacher salaries, schools spokesman John Torre said.

Schools nationwide are enjoying the dramatically lower pump prices. In Mesa, Ariz., schools are saving $50,000 a month. Schools in South Bend, Ind., expect to trim nearly $386,000 from their annual fuel costs. Mobile County, Ala., schools are looking at a $247,000 savings.

It adds up. The nation’s schools could see $2 billion in gas savings during the current fiscal year, according to calculations by Trace Urdan, a Wells Fargo analyst.

Throw in another $1.65 billion in savings for heating fuel this fiscal year, Urdan wrote, and that could spur additional spending on education, which could be good news for textbook publisher Houghton Mifflin Harcourt or online learning company K12.

Everyone has been cheering lower gas prices. It was an applause line in President Obama’s State of the Union speech, when he heralded that the typical family should save $750 at the pump this year.

The national average for a gallon of unleaded gas stood at $2.07 earlier this week, according to the U.S. Energy Information Administration. Early last summer it was $3.65. That’s a drop of 40 percent.

Most school buses run on diesel – and the price drop for diesel has been less dramatic, about 25 percent over the same time period, to a national average of $2.93.

In South Carolina, where the state owns the public school’s 5,200 school buses, every 10-cent drop in diesel prices led to $1.2 million in reduced annual fuel costs, said Mike Martin, executive director of the National Association for Pupil Transportation. Martin estimated that the nation’s school buses travel 4.5 billion to 5 billion miles a year. So the savings really do add up. But he cautioned against expectations that this would lead to a boom in school spending on education. A few years ago, a sudden spike in gas prices caught some school districts short.

“It’s nice to have this,” he said, “but all it really does is gives some breathing room.”