I'll hazard a guess that because it's a smaller vocational school for black kids with admittance standards, it puts them into a lower tier high school sports category, like AA instead of AAA or higher with the big high schools. Thus they are competing against smaller Catholic or private schools in their league, but they have a pool of black sports players the private schools do not have to draw upon for talent.

That's what I'm guess from their wikipage and knowledge of HS sports.