Jim Davis/Globe Staff

Blake Evitt, an instructor with Parkour Generations Americas, led students up stairs during a morning session at Somerville High School.

Jim Davis/Globe Staff

Participant David Kovin ducked under a tree branch while running on a wall.

Jim Davis/Globe Staff

Daniel Abraham, Cristian Lopez, David Kovin, Blake Evitt, and Rachel Kelly negotiated railings

Jim Davis/Globe Staff

Blake Evitt lead students up stairs.

Jim Davis/Globe Staff

Rachel Kelly crawled up some stairs.