I worked there until 10 years ago and it was quite rewarding. (In fact this interactive uses some of the "lab" framework code I worked on.)

The founder was inspired by Concord (Massachusetts)'s history of progressive educational experimentation, going back to the transcendentalists (Emerson, Thoreau).

They're based in Concord but they also have a Bay Area office, after merging with the nonprofit org that built CODAP (https://codap.concord.org/)