Everything you need to understand or teach Killers of a Certain Age by Deanna Raybourn.
Killers of a Certain Age, by Deanna Raybourn, is a mystery novel about four women dubbed Project Sphinx. The women were trained in the 1970s as an elite, extra-governmental assassin force called the Museum. A second timeline in this novel picks up when the women are around age 60, facing all the normal trials of aging while fighting off an order from the Museum to kill all four. They protect themselves, work through the conspiracy, and assassinate those who have lost sight of the organization's true goals. The novel examines the life of an assassin, the effects of aging, one's true identity, the inevitability of change, and justice versus law.