At least two schools have introduced summer timings and are ending their classes early.
St James' School and Calcutta Girls' High School have introduced summer timings and will continue with early dispersal till they close for the summer vacation, officials at both institutions said.
At St James' School, classes are over by noon, and at Calcutra Girls' High School, by 12.15pm.
Classes at Calcutta Girls' High School are starting at 7.25am, instead of 8am. Both schools are following staggered dispersal, from 10.30am.
St James' School has been following the summer schedule since Friday and Calcutta Girls' for about a week now.
"We have to understand that it is going to be sultry. There could be one or two spells of rain that can temporarily cool down the weather, but that won't sustain," said Terence Ireland, principal, St James' School.
Many schools this year started the session in the first week of April, having brought it forward by seven to 10 days. Some schools reopened after the session break even earlier, in the third week of March.
For the last two years, schools have been having an extended summer break or shifting to online classes during the period because of excessive heat.
Several teachers said students find it tough to attend classes when it is too hot. Even schools with air-conditioned classrooms face this problem when a room is packed with 30 to 45 students.
"The situation become more difficult in the second half, when the children are often seen struggling to concentrate on the text or what is being taught in class," said Joseph Chacko, senior coordinator, St James' School.
But not all schools are changing their timings or having any plan to do so.
St Augustine's Day School Shyamnagar has not tweaked its timings but have erected a shed outside the school.
"We took permission from the local authorities to build the temporary shed for guardians who come to pick their children up. They can at least wait there instead of being directly exposed to the sun," said Rodney Borneo, principal, St Augustine's Day School Shyamnagar.
The school started its new session in the third week of March.
"We want to continue with the regular timings. There was a reason why we started early and that reason was to get some work done before we close for summer," he said.
Several schools have suspended outdoor activities to limit the students' direct exposure to the sun.
Physical training classes are being conducted indoors or under a shed.
"We are only continuing with swimming and basketball (which is played under a shed)," said Ireland.
In some schools, children are being discouraged to go out during the lunch break.