Swedish environmental activist Greta Thunberg (left) takes part during the Climate Strike in NYC.

Kids protesting during the Global Climate Strike march in NYC.

Thousands of teens and pre-teens jammed Foley Square Park in Lower Manhattan on Friday to demand an end to fossil fuels ahead of a United Nations “Climate Action Summit” next week.

The kids chanted slogans including, “Hey hey, ho ho, climate change has got to go!” and “What do we want? Climate justice! When do we want it? Now!”

Some also held hand-lettered signs that said “You can’t breathe profits” and “Destroy the patriarchy, not the planet.”

An NYPD cop estimated the crowd size at around 40,000.

The gathering was set to precede a march to nearby Battery Park for the city’s “Climate Strike” youth rally, one of similar events being held around the globe.

The Department of Education allowed students with parental permission to skip school and attend the protest, which will feature a speech by 15-year-old Swedish activist Greta Thunberg.

“Right now is the time to strike. We don’t have much time left,” said Jack Brady, 15, who attends the Clinton School in Chelsea.

“Climate change is real. Temperatures are rising, sea levels are rising, it’s getting hotter, winters are getting crazier.”

Earlier, Brooklyn Borough President Eric Adams used a bullhorn address a huge group of kids who gathered on the steps of Brooklyn Borough Hall before heading to Manhattan.

“If you go in history, the globe has never been changed by adults. It has always been young people,” he said to cheers.