Three-year-old Derrick thinks about his daddy a lot. Maggie, his teacher, can tell because nearly every day she sees him pretending to be a soldier. When his dad’s National Guard unit was getting ready to deploy to Afghanistan earlier in the year, Derrick would act out packing a suitcase, saying goodbye to his pretend family, and getting all his gear ready to “go to work” – gear that included a helmet and a gun. When his dad was injured in …