The mother of one of the 26 victims of last year's Sandy Hook Elementary School massacre has written a powerful letter to the teachers of America. Nebla Marquez-Greene had two children attending Sandy Hook Elementary that day. Her daughter, 6-year-old Ana Grace, was killed in the massacre, but her son was uninjured in the attack. Her letter, which was posted on the Education Week website is powerful, and gut-wrenching, and encouraging all in one. Read it after the jump.