Youths from more than 150 countries ditched the classroom Friday and hit the streets to urge world leaders to take serious action against climate change.

Millions of young people marched in places from Moscow to Manhattan, where many showcased their concerns through witty protest signs. The global march comes just ahead of a U.N. climate summit Monday. We scoured Twitter, combed the wires and chatted with a few of our staffers on site, and rounded up some of the best signs we saw.