KINGMAN, Ariz. — A school district here is struggling during the hot weather with a shortage of school buses with air conditioning as students returned to school on Wednesday.

As Kingman Unified School District No. 20 students came home from their first day of school, some parents noticed that their children were having issues due to the heat, Daily Miner reports. A mother of an elementary school student told the newspaper that her daughter had ridden a school bus that didn’t have air conditioning for 50 minutes when it was 107 degrees Fahrenheit outside.

Roger Jacks, the superintendent for the district, informed parents in a letter that was posted on the school district’s Facebook page on Thursday that of the district’s 54 route buses, 18 don’t have air conditioning. Jacks explained in the letter that although the school district has only bought school buses with air conditioning for years, including the 20 new buses purchased over the past year, the fleet still includes some older school buses without it.

The air-conditioned buses that the district does have are used for special-needs students and students who travel longer distances, Jacks added in the letter.

Adding to the problem is that air-conditioning units on some of the earlier model buses are more maintenance-intensive and break down on a regular basis, he explained in the letter. Mechanics worked over the weekend to repair the air-conditioning units.

“Our priority goal is a fleet of all air-conditioned buses,” Jacks said in the letter. He told Daily Miner, “We do apologize for the bad situation and bad heat with no AC buses.”

The district office has asked schools to notify students to drink plenty of water during the day and during the ride home, Daily Miner reports.