Tyler Gardiner, one of the leaders of Watertown High School’s successful boys hockey team, will keep his dream of playing in college alive by playing for a year with the Boston Junior Rangers of the Eastern Hockey League. Gardiner recently signed with the Junior Rangers’ Premier team, the higher of the two levels. He said this is a typical path to playing hockey in college. “Most colleges don’t take kids under 21. They go to the juniors or have a year of prep school,” Gardiner said.