I don't think that's what they're saying.

Anacostia High School in Washington DC has zero percent of students meeting expectations in Math, yet its funding per student is twice that of nearby districts that perform much better. Lebron James' I Promise Academy is similarly very well-funded both for in-classroom and wraparound services, and it's one of the worst schools in the state of Ohio. It is increasingly evident that we cannot improve student outcomes in failing schools simply by funneling more resources to those schools. Students who come from households who do not value education not only will not learn, but will also likely sabotage the education of the others in their schools. It is probably more effective to give direct cash payments to struggling families than to struggling schools.

https://profiles.dcps.dc.gov/Anacostia+High+School

The reality, which politicians will never admit out loud, is there is a population of K-12 students who 1. will never become educated to any measurable standard, and 2. disrupt the education of everyone around them. You could give unlimited funding to a school, and these kids will not learn. You could assign a huge staff of dedicated top-educators to each class, and it won't make a difference. You could isolate them from everyone else, each individual into a dedicated classroom with that staff of education PhDs all to themselves, and they will not learn. They will either graduate high school not meeting the standard, or they will drop out before they graduate. You can't force education on someone whose parents, peers, and surrounding environment don't value it.