From the DCI.org web site, here's a great description of life in an "old time" drum corps circa 1968 in Wisconsin. The following quote reminds me of my experience in the Ambassadors from 1979 to 1983. Of course even then the school music programs were less than they were in the 60s and local support in the Aurora and Newmarket was good but not overwhleming. I remember that the music teacher at Huron Heights S.S. in Newmarket said of drum corps: "They play at two volumes: loud and louder". He was enlightened; he knew what a drum corps was.
At that time, for those more "schooled" in music, drum corps was considered not "real" music, and the participants weren't considered "musicians." It was more of a "blue-collar" activity for kids who would otherwise have had little else to be involved with, or had gotten themselves into trouble. There was far less variety in the musical selections and the corps had far inferior equipment and no big name arrangers or instructors - those jobs were usually filled by former corps members who stuck around after they aged out.