The Toronto District School Board says its staff are “doing their very best” to keep kids cool during an unusual September heat wave amid concerns from parents and students about sweltering classrooms.

TDSB spokesperson Ryan Bird told CTV News Toronto on Monday that staff are reminding students to stay hydrated and cutting back on strenuous activities during the hot weather, but little else can be done to alleviate the conditions.

“To install full building air conditioning at all the schools that don’t currently have it, we’re talking hundreds of millions of dollars, not to mention the electricity costs, maintenance and repairs,” Bird said.

“In the meantime, our staff is doing the very best they can whether it’s using fans, getting air circulating, staying hydrated... That sort of thing.”

Toronto and areas across southern Ontario have been grappling with an unprecedented bout of sky-high temperatures over the past week.

The city’s top doctor extended a heat warning Monday morning ahead of a daytime high of 31 C, feeling more like 40 with humidity.

According to Bird, only 125 of the TDSB’s 584 schools are fully air conditioned.

Of the remainder, at least 150 are completely without air conditioning.

“Yes we’re doing all that we can, given the difficult circumstances, to keep students and staff as cool as possible. But if someone has asthma or a special medical concern or they’re particularly susceptible to this heat, we want to know about it,” Bird said.

“We want students and parents to talk to staff so that we can accommodate as best we can.”

Meanwhile, the Elementary Teachers’ Federation of Ontario (ETFO) says it’s time that the government does more to address the uncomfortable conditions in classrooms.

In a news release issued Monday, the ETFO urged the province to take immediate action at elementary schools, in particular, which they say are least likely to have air conditioning.

“Students and teachers in many classrooms are subject to unbearable conditions with temperatures over 30 degrees. That takes an unacceptable toll on teaching and learning,” ETFO president Sam Hammond wrote in the release.

The group wants the province to fund the installation of air conditioning or "heat reduction systems” in elementary schools and set indoor temperature limits where schools would close if conditions surpassed them.

While the ETFO acknowledges that installing air conditioning at all schools would be costly, it says that “not fixing the problem” would acquire more “significant costs.”

“Our changing climate is sending a strong message that the Ministry of Education needs to take action,” Hammond wrote. “Too much student learning will be lost the longer the Ministry delays.”

Bird said he doesn’t believe installing air conditioning at TDSB schools is financially possible “now or in the future.”

“I’m seeing on our social media accounts and elsewhere that we do have concerns from parents and students and then we also have some that understand that it’s hot and there’s not a lot we can do,” he said.

“Our best advice is to do what you would on any hot weather day – wear light clothing, drink lots of water as best you can and just know that in the meantime, our staff are honestly doing the very best they can to minimize the impact of this heat on our students.”

Kent Yee, the principal of Adam Beck Public School in Scarborough, told CTV News Toronto that teachers have been instructed to remind students to drink water every half an hour.

“We always remind students to come to school with water bottles and we also have fountains in our schools, so we remind them to hydrate themselves…We also make morning announcements,” he said.

“Other things we have at our school are fans in each classroom.”

Some parents of students heading into Adam Beck Public School this morning said they’re not concerned by the hot weather.

“The schools are so old so they’re not equipped to have air conditioning so they just make the best of it,” one parent said. “I’m a teacher, so I know how it is, it’s sweltering but I think that in many places around the world they do learn in hot conditions. So it’s possible.”

Others say it’s been hard to overcome.

“My daughter is on the third floor of this school and she says it’s very hot,” another parent said.

“It’s sweaty,” her daughter chimed in. “It’s even more hot than outside.”

But it's not over yet -- Toronto still has a few more days of hot weather ahead.

According to Environment Canada, Tuesday will hit a high of 31 C with a humidex value of 39.

The possibility of rain brings temperatures down slightly on Wednesday -- to around 29 C – but the real relief comes on Thursday where a high of 21 C is forecasted.