The new timing is likely to be implemented from Wednesday, the official told IANS.
All classes up to eighth will close at 10.30 a.m. and classes from ninth to 12th at 11.30 a.m., he said.
Once the summer capital of undivided Bihar, Ranchi has been experiencing temperatures well above 40 degree Celsius since April 1.
On Monday, a school girl reportedly died here due to sun stroke.
About 15 deaths in Jharkhand have so far been attributed to the intense heat, with temperatures in Jamshedpur and Daltanganj touching 45 degree Celsius.
There is also acute water crisis in Ranchi, Jamshedpur, Daltanagnj and some other parts of the state.(IANS)