After working in shops for many years and working with mechanics that went to a school then became a mechanic I would say become a mechanic first then after a year or two of working under a good mechanic or service manager take the classes you will learn more that way. the schools tell you how to do it by the book which in real world shops isnt always possible or viable but you will learn better ways to do somethings and get some sharpening of your skills as a mechanic.