I 'rebuilt' two small school programs in my career. The first was in a school like I described - everything they did was successful, but band had fallen on hard times. It was very easy to turn that program, and once the community saw that we were doing things the right way, kids came back to the program in a flood.
The second was at a school where nothing was successful. They were the whipping boy in every sport and everything else. Even though I started with more kids, and people got excited about the massive improvement they saw right off the bat, growth beyond 'just okay' was tedious and painfully slow. We never did really get over the hump because while we grew and became one of the most successful programs in the school, we were still behind the other programs in the region.