WASHINGTON — Three days after six teachers and 20 students were killed by a rampaging gunman at a Connecticut elementary school, an 8-year-old Maryland boy pulled out a sheet of paper and wrote President Barack Obama, asking for “some changes in the laws with guns.” “It’s a free country but I recommend there needs (to) be a limit with guns,” Grant Fritz said in the Dec. 17 letter. “Please don’t let people own machine guns or other powerful guns like that.” In the days after the Dec. 14 shooting in Newtown, Conn., children around the country apparently had the same …