School officials in North Vancouver say it's an unfortunate coincidence that thousands of students will have the day off during 4/20, the annual marijuana protest that sees massive crowds gather to smoke pot.

Classes at four of the city's high schools will be empty on April 20 thanks to a professional development day that was planned a year in advance, according to the North Vancouver School District.

District principal Brad Baker said by the time officials realized the problem, it was too late to reschedule.

"In essence, because the dates are picked by a committee it was next to impossible the change the date for this year," Baker said.

But the district never intended to encourage students to attend the massive marijuana protest, which is being held at Vancouver's Sunset Beach for the third year in a row.

"We were not promoting the 4/20 event," Baker said. "We obviously want to have our students at the high schools interact with their own community. There's obviously lots of activities to do on the North Shore, and we'd rather have them do that."

On Tuesday, officials sent an email to parents alerting them about the poorly timed professional day, and suggesting they have a discussion with their children about drug use.

"As part of the ongoing education of substance use, we encourage conversations to occur at home regarding the use of cannabis and other substances," it read.

And North Vancouver isn't alone in the blunder. Students at other schools in Delta and Coquitlam will also have that day off, though they would have further to travel to reach the West End.

Vancouver's growing 4/20 protest is now highly commercialized and bears a strong resemblance to music festivals, complete with a large stage where bands play. There are also dozens of booths selling merchandise, paraphernalia and marijuana in various forms.

There are always some underage attendees, including a 14-year-old who was treated in the emergency department at St. Paul's Hospital during last year's event.

The hospital took in 10 patients under the age of 20 in connection with the protest, though none of the youths actually had to be admitted. Most felt sick after ingesting edible pot products, according to health officials.

Dana Larsen, one of the 4/20 organizers, said vendors are instructed not to sell to minors, and he's not worried that more high schoolers from North Vancouver could show up this year.

"Not really. Next year it's going to be on a Saturday so there's not going to be any school for anybody at all," he said.

Larsen acknowledged some teenagers will most likely get their hands on pot, but argued it's no more prevalent than underage drinking is at all-ages concerts that serve beer.

"I'm sure that there's some minors that are able to access cannabis on 4/20, just like some minors are able to get alcohol at the many all-ages beer gardens and other alcohol events," Larsen said.

The Vancouver Police Department said it will have a presence at this year’s event, as usual, and may be dispatching more youth squad members.

The North Vancouver School District offered a number of links for any parents looking for more information on drug use.

With files from CTV Vancouver's Penny Daflos