Standard Operating Procedure in Texas.
Allen is just north of -- and is the 21st century version of -- Plano, where I lived during the 70's and 80's.
When I arrived, Plano was the AA champion; several years of growth later, they were the AAA champion -- for several years. Then, soon after, they were competing for the AAAA state title. Which they won, soon enough.
To maintain that winning streak, the town voted for a bond issue that -- rather than split the town into two high schools -- created two Grade 9-10 schools and one massive Grade 11-12 school. My son graduated in a class of 2,200, for example.
The express purpose was to maintain a winning football team that could challenge for the state title, year after year. And, at the same time, keep the entire community focussed around that school's success.
It worked.
As an aside, the three best football games I ever saw at any level were in the 1977 Plano championship run. Others on this board will recall them: Quarter-finals: Plano 29, at Highland Park, 28 (miraculously coming back from a 0-28 deficit in the 4th quarter); Plano 3, Odessa Permian 0 (at Lubbock, in an icy north wind...the FG was in the first series...and, with the wind, bounced over the goalpost). And, finally, I had the pleasure of seeing the Plano Wildcats win a state title against the Port Neches-Groves Indians ("Hot boudin. Cold cous cous. C'mon Indians, poosh, poosh, poosh!") before 70,000 rabid fans at Cowboys Stadium.
Yeah, H.S. football in Texas is serious business. And a lot of fun. Everybody should experience it.
The thing is, the Plano High Schools share the stadium, this stadium is for one school.
Stephenville, Brownwood, Odessa Permian, Abilene Cooper, LaMarque, and Lake Travis are some others but I've left out dozens of other excellent HS Texas programs that are legendary.