Students at one downtown Toronto high school chanted "Doug Ford has got to go" as they walked out of class on Thursday, joining students at hundreds of Ontario schools who oppose changes to the province's education system.

The walkout at Bloor Collegiate Institute was among hundreds by both elementary and high school students organized on social media, mainly Instagram, with the hashtag #StudentsSayNo.

In London, Ont., dozens of students from H.B. Beal Secondary School lined the sidewalks for a protest, before marching to city hall to continue the demonstration.

All these <a href="https://twitter.com/hashtag/ldnont?src=hash&ref_src=twsrc%5Etfw">#ldnont</a> students are ditching class. <br><br>Students at H.B. Beal Secondary School walked out of class this afternoon as part of a province-wide protest against changes and cuts to the education system. <a href="https://t.co/fjbttgBzJq">pic.twitter.com/fjbttgBzJq</a> —@Hala_Ghonaim

Students also marched out of Mississauga Erindale Secondary School, just west of Toronto, carrying signs, many critical of Ford. There were also walkouts in other cities, including Ottawa, Windsor, Thunder Bay and Hamilton.

At Queen's Park, Ontario Premier Doug Ford criticized the walkouts, saying the students were being used as pawns by "union bosses telling the teachers and the students what to do."

Viral social media post led to walkout

A viral post by Natalie Moore, a Grade 12 student at Listowel District Secondary School in Listowel, Ont., started the movement, and it quickly snowballed as her friends around Ontario shared it in their own Instagram stories.

Moore said she was deeply troubled by the Progressive Conservative government's decision to increase average required class sizes in intermediate and high school grades in the province.

"I emailed my MPP, and when I didn't hear back from him, I really wanted to do something," Moore told CBC Radio's Metro Morning on Thursday.

"I felt like students weren't aware, or they wouldn't do the research into the cuts. They might hear about them, but I didn't know how much detail they would know."

We aren't doing this to skip class. We aren't doing this because teachers told us to. We are doing this because we are angry. we will not sit back and watch our education be ruined by adults who see us as nothing. <a href="https://twitter.com/hashtag/StudentsSayNo?src=hash&ref_src=twsrc%5Etfw">#StudentsSayNo</a> —@melino_juliana

Amina Vance, a Grade 12 student at Western Technical-Commercial School in Toronto, helped Moore organize the protest. She said bigger class sizes — which school boards have warned could result in job losses for teachers, and decreases in the kinds of courses offered at individual schools — will be devastating, particularly for students with special needs or other challenges.

"We are astounded they would do this to us, especially to marginalized students, who are already struggling in our school system," she said on Metro Morning.

"We are showing them that students are informed, that students are angry, and that students are ready to make a difference."

You can listen to the whole interview with Moore and Vance below:

During question period at the Ontario legislature on Thursday, Ford said the walkout should have been stopped.

"Our teachers have a responsibility to the parents, to the students, to make sure they stay in the classrooms and teach the students," he continued.

"It's absolutely shameful they're using our students for a bunch of pawns," Ford added.

A student posted this image of a protest sign on Twitter. (@kayluahs/Twitter)

Schools preparing for protest

Individual schools and boards in the Toronto area sent letters home to parents saying that administrators were aware of the planned walkout and that they would work to ensure student safety, while noting that the protests are not school-sanctioned events.

"As a school board, we encourage students to be well-informed about issues in our society, to think critically, and to express themselves respectfully and responsibly in articulating views they may have," wrote the Toronto District School Board, the largest in the province.

The protest action comes weeks after Ontario's Progressive Conservative government announced considerable education reforms. The changes include increased class sizes for intermediate and secondary grades, as well as new math and sex-ed curricula and mandatory e-learning modules.

we walk out today. to young people: be brave, be bold, do not let them tell you what you know or what you deserve. get up. walk out. we got this. 💓 <a href="https://twitter.com/hashtag/StudentsSayNo?src=hash&ref_src=twsrc%5Etfw">#StudentsSayNo</a> —@rayneydaes

The average class size requirement for Grades 9 to 12 will be adjusted to 28, up from the current average of 22, while the average class size for Grades 4 to 8 will increase to 24.5, up slightly from 23.84.

The decision to increase some class sizes has drawn sharp criticism from some educators, as well as from unions and some parents.

Ontario Education Minister Lisa Thompson ignited controversy when she said in an interview last month that bigger classes will make students more resilient and more prepared for the workforce.

Moore said she believes Thompson's comments "are an excuse to cut funding and balance the budget.

"That shouldn't come at the cost of our world-class education system."

Thompson characterized the walkouts as "political stunts" and blamed teachers' unions for "not discouraging" them.

"On a day when we reached out to begin good-faith consultations with Ontario's teachers, we instead are seeing Ontario teachers' unions condoning a student walkout at schools across the province," she said Thursday in a statement.

"Our government will not be distracted from making the necessary reforms Ontario needs."

today, thousands of kids are going to walk out in protest of doug ford's education cuts. thousands of kids have decided that staying silent isn't good enough for them. thousands of kids have decided they deserve a voice. <a href="https://twitter.com/hashtag/studentssayno?src=hash&ref_src=twsrc%5Etfw">#studentssayno</a> —@deelxn

For her part, Vance said larger class sizes will mean that the students who need help the most simply won't get it.

"I see in my school every day, teachers are front-line on the mental health crisis. And teachers are dealing with those crises, student crises, every single day."