It was a favourite of mine.
A teen amature photographer is walking home from school, past his hot high school teacher’s house. Looks in the window, see’s her screwing one of the male teachers. Takes photos, blackmails his teacher into sex. His sister finds out, and wants in, she wants the hot male teacher. Hot hi-jinx ensues…
Source: reddit.com/r/Erotica/comments/40qp31/request_looking_for_an_old_beeline_or_greenleaf