TORONTO -- Fewer parents kept their kids out of classes at a Toronto public school Wednesday in protest of Ontario's new sex-education curriculum, but the school itself was vandalized overnight.

The Toronto District School Board said about 1,000 of Thorncliffe Park's 1,400 students were in classes Wednesday, up from 700 on the first day of school on Tuesday.

The board also said the words "shame on you" were spray-painted on the walls of Thorncliffe Park and the neighbouring Fraser Mustard Early Learning Academy in an apparent protest of the updated sex-ed curriculum.

"Of course I'm concerned. I was very dismayed to hear about the vandalism," said Premier Kathleen Wynne, whose riding includes Thorncliffe Park. "I was dismayed yesterday when kids were being kept home from school."

Vandalism is not a normal form of civil protest and takes the opposition to the updated sex-ed curriculum to "a whole different realm" that will require a police investigation, added Wynne.

"To create the kind of anger and hostility that's being created I think is very detrimental and I think it's a dangerous precedent to set," she said.

"What really makes me feel very distraught about this is the kids who are caught in the middle, little children who are going into that school today won't understand why that has been written on the walls."

Wynne said she met several times with parents from Thorncliffe Park and found some really didn't know they had the right to take their kids out of lessons they object to without taking them completely out of school.

"We're paying really close attention to what's going on, and it's not just in Thorncliffe Park but in other small pockets of the (Greater Toronto and Hamilton Area)," she said. "I really, really hope that in a very short time things calm down, that kids will be in school.

The government talked to dozens of interest groups as it developed the new curriculum and sent out surveys to one parent at each elementary school, but fewer than half of them responded.

That added fuel to opposition complaints that the Liberals did not consult parents widely enough on the changes, complaints Wynne dismissed by saying the curriculum was the "most consulted upon" document in Ontario history.

"There was an outreach to the 4,000 school council chairs in the elementary schools," she said. "We can't force people to take part in consultations."

Under the changes, Grade 3 students will learn about same-sex relationships, kids in Grades 4 and up will learn more about the dangers of online bullying, while the perils of sexting will come in Grade 7.

Lessons about puberty will move from Grade 5 to Grade 4, while masturbation and "gender expression" are mentioned in the Grade 6 curriculum.

Wynne again vowed the Liberal government would not back down on implementing the first update to the province's sex ed curriculum since 1998.

"If we're going to keep kids safe in school they need to have information, they need to understand what they're seeing on their smart phones and Snapchat and all of the machines they have, so we absolutely have to have an updated health and physical education curriculum," she said.

"It's about helping children to understand differences among themselves and to have the information that they need so there will be less bullying, less ostracization, and there will be more understanding of who they are as people."