Also, that other district you mention had had JH/MS kids in band, too, building the program up over years. I went to college out that way and had classes that observed at that middle school *years* before that SMC champion year. It didn't spring up fully-formed out of nowhere one year. They didn't create a program out of nothing and expect to win. That's simply not realistic.
And yes, the immediate success of that HS program speaks to the quality teaching that was going on at said JH there, and their ability to build up that program. There have been great things going on in that school now for well over twenty-five years. That's what "pedigree" is. A history of success creates future success.
tl;dr: That other district's kids weren't starting a marching band completely from scratch. OP is. Depending upon how long OP has been at their school, it may not blow the doors down right away. And that's OK.