It’s about 4 p.m. in Room 228 at Skyview High School in Billings, Montana, and resource teacher Deb Roesler is explaining her “action plan.” In the coming days, when she returns to her middle school across town, this white, middle-aged, rural Montanan will invite a student who doesn’t look like her to eat lunch together. “I’ve been in the biggest groups all day. I’ve never been in a small group,” she says, referring to the “identity groups” that have formed…