I dont remember what grade I was in. But I'd guess between 13 - 19 years ago. I just looked Nature's Classroom up though and they've been around for 50 years.

Grew up in Mass. I remember one year I had to go to a multi-night field trip called nature's classroom. One the things we learned about was the underground railroad. They lined us up in rows of 2 and walked us like we were slaves while calling us negros and made whip cracks. They warned us that it would be Intense beforehand and a few kids cried who were allowed to fall out. It was intense but it was eye-opening of just a fraction of what slaves went through.

This however clearly had a bias of the participants color, did not get approval or suggestions from other staff. Or have a place for students to disengage from participation if they were yo troubled by it.