We spent a day with the 15-year-old activist who led the Vancouver climate strike

Just hours before she helped lead a march of 100,000 people through Vancouver, Lilah Williamson had to write a social studies exam.

By 10 a.m., the 15-year-old girl was done the test, plus choir practice. She boarded the SkyTrain and arrived at city hall at around 10:30 a.m. By then, a crowd had already started to form on the front steps.

Four hours later, Williamson would address a crowd of thousandswho turned out for a climate strike organized by the teen climate justice group Sustainabiliteens.

It was part of a series of global strikesinspired by 16-year-old Swedish student Greta Thunberg, who began skipping class on Fridays to protest a lack of action on climate issues.

Williamson, one of the founding members of Sustainabiliteens,has cared about climate change for years, but said that the forest fire smoke that blanketed Vancouver during the summer of 2018 motivated her to act.

The group spent four months planning the climate strike on Friday.CBC photographer Maggie MacPherson spent the day with Williamson as the teen helped co-ordinate the massive event.

Williamson stays behind for a moment. In shock of how many people attended and also how things were not going as planned.

Williamson had expected to lead the march with the other Sustainabiliteens. Without them being at the front, she wondered if the thousands of people would end up at the right location.

Several of the Sustainabiliteens jumped into a shuttle to try and beat the marchers to the end destination.

The shuttle was stuck in traffic, so the Sustainabiliteens jumped out and walked the rest of the way to the final destination.

Williamson says the climate crisismay be the biggest crisis humanity has ever faced.

"The power of people is so strong and human beings are really smart," she said. "If we all work together and make it a priority, we can turn it around."