Life Lessons by Kaje Harper

Mac’s three goals: keep Tony safe, catch the killer, don’t come out.

Tony Hart’s a dedicated teacher, though he’s not much older than his high-school students. Between his profession, a few good friends, and plenty of books, he’s content with his quiet life. Then the murdered body of another teacher falls into the elevator at his feet, and Tony’s life becomes all too exciting.
Jared MacLean is a homicide detective, widowed father to a young daughter, and deeply in the closet. But from the moment he meets Tony’s blue eyes in that high school hallway, Mac can’t help wanting this man in his life. Mac’s not out ― can’t afford to be out ― but Tony makes him want the impossible.
Mac isn’t the only one with their eyes on Tony, though. As the murderer tries to cover their tracks, Mac has to work fast or lose Tony, permanently.

(This is a rerelease of the 2011 original with light editing.)