And you can talk all you want about band sizes getting smaller - take suburban random ISD. Thirty years ago, that ISD had 1 or 2 5A schools, with 200 kids in each band. Now, that ISD has four 5A or 6A schools, with 150 kids in each band. Those bands look smaller on the surface, but RandomISD has 600 kids in HS band whereas 30 years ago they had 400. How many ISDs have opened a new high school, or two, or three in the past thirty years? Or have shot up in classifications? In the D/FW and greater Houston suburban areas (the areas with which I'm most familiar) the answer is nearly all of them.
New schools, just in Tarrant County, since 1995 (30 years): Northwest ISD (2 campuses), Keller ISD (3 campuses), Grapevine-Colleyville ISD (1 campus), Crowley ISD (1 campus), Birdville ISD (1 campus), Everman ISD (1 campus), Arlington ISD (1 campus), Mansfield ISD (4 campuses). Eagle Mountain-Saginaw HS (2 campuses, opening a 3rd in 2 years). Kennedale opened its first high school in 1998 - before that, those kids went to Arlington schools.
And in that time, Southlake Carroll went from a 3A school to a 6A, Aledo went from a 3A to a 5A, Godley from a 2A to a large 4A. Only HEB ISD really hasn't "grown" much as a district, and they're totally built out and landlocked. Lake Worth and White Settlement are growING but haven't grown as much yet, as the population growth has been in the mid-cities and not the west side of the county.
This is just Tarrant County. Dallas County has had growth. Collin County - twenty years ago, Frisco was ONE 3A school. Now they're a dozen 5As. Plano had 2 schools, now they have 3, and are among the largest high schools in Texas. Allen was a small 5A, and is now *the* biggest school in Texas. Think about the Houston area. Cypress-Fairbanks has a dozen or more high schools. Katy ISD has about the same. Each individual school may not have a 300-piece behemoth of a band the way some schools used to, but there are MORE schools now than in years past.
Every year at TMEA we hear at the general session about the number of participants in the All-State process. That number (not counting Covid influences) hasn't gotten smaller at any point during my career.
You can talk about money all you want, and that's a valid discussion, but the fact is, there are more bands, more schools, and more kids participating than ever, EXCEPT for the past two years, which has a huge C19 influence on it.