Cambodia has shortened the school day by one hour to help students cope with a heatwave that has pushed temperatures as high as 42C (107.6F).
Education minister Hang Chuon Naron signed the rule into effect on Monday, and it will remain in place until the cooling rains begin. The rainy season normally starts in late May but could begin later this year, he said.
The new rule deducts 30 minutes from the beginning and end of each school day, said education ministry spokesman Ros Lina.
Most schools in Cambodia, like elsewhere in the region, have no air conditioning.
The next long break for Cambodian students will be from August to October.
School authorities throughout Cambodia were also ordered to be aware of heat-related illness, such as heat stroke, and advise students to drink more water.
Countries across south-east Asia are enduring a heatwave that scientists say is triggered by El Nino, a warming of parts of the Pacific Ocean that changes weather worldwide and tends to push up global temperatures. El Nino has also been blamed for causing the worst drought in decades across the region.
In neighbouring Thailand, the average peak temperature each day this month has been above 40C (104F), with the mercury spiking one day to 44.3C (111.7 F) – just short of the all-time record.