Students are being asked to carry umbrellas or caps to be worn during dispersal and teachers are being told to keep themselves hydrated because "talking continuously" in a classroom can be a strain too.
The first day of the week was exhausting for students and teachers as the weather continued to remain hot and stifling.
"We have not changed our timings but we have asked students to carry umbrellas and caps," said Anjana Saha, principal of Mahadevi Birla World Academy.
Wearing caps or using umbrellas during dispersal can at least shield them from the direct sun, she said.
For many schools, this is the third week since they started the academic session but the weather is impacting classroom transactions, many of them said.
An English teacher in a south Calcutta school noticed a visible change in the countenance of children.
"I went to teach Class VII at 10am. When I went to the same class again at 12.30pm, the children looked tired and lethargic and I wondered whether they were at all understanding what was being taught," said a teacher.
Some schools have suspended the morning assembly and are avoiding large gatherings.
"For assembly, the children have to come down from their classrooms and again go up the stairs. We are trying to avoid that because it will make it more tiring for children," said Apala Dutta, principal of Birla Bharati.
"As it is, children are getting tired more easily and there is general slowness around (because of the weather)."
The school has told teachers to allow children to drink water even when the class is on. "They do not have to seek permission and we are being relaxed about rules," said Dutta.
The discomfort level among teachers is also high as many of them have to take back-to-back classes.
"Teachers have to keep themselves hydrated because talking continuously can be a strain in this heat," said Terence Ireland, principal, St James' School.
Across schools, teachers are expected to teach standing, something that could only push up the exhaustion level. "We are not being strict now," said Ireland.
In many schools, teachers are out for evaluation of board papers and those who are in school are having to take extra classes.
"The weather is making them exhausted, especially if they have four or five consecutive classes," said Terence John, principal, Julien Day School Kalyani.
At least two schools, St James' School and Calcutta Girls' High School, are following summer timings and the classes are ending early.
A couple of other schools said they are contemplating a change and will decide after watching the weather for a day or two.