VIRGINIA HAS made strides in enabling poor children to attend pre-kindergarten classes, which are widely credited with improving learning skills, including reading readiness. But some of the state’s biggest school districts, particularly in Northern Virginia, have been slow off the mark. The worst laggard, by far, is Prince William County.

With 85,000 students, Prince William is the second-largest school system in Virginia and among the 40 biggest in the nation; its annual budget is nearly $1 billion. Yet it has managed to find funding for just 4 percent of the 4-year-olds who are eligible under a state-subsidized program to attend pre-K classes. No other large school system in Virginia comes close to such disregard for the disadvantaged.

In the process of ignoring those eligible poor children — more than two-thirds of them minorities — Prince William is turning its back on more than $6 million in state funding. To get that money flowing from Richmond, the county would need to spend just $3.6 million from its own schools budget. That’s less than 1 percent of what it allocates annually for K-12 education, and it would pay for approximately 1,590 4-year-olds to get a leg up on school.

That sounds like an excellent return on investment, but the county pleads poverty. Neither the Republican-led Board of Supervisors (which is all white) nor the Republican-led county School Board seems moved by the fact that Prince William’s least advantaged children are getting a raw deal.

Nor is the state blameless. Just before the recession hit, then-Gov. (now Sen.) Timothy M. Kaine bumped up the funding for Virginia’s pre-K program to $6,000 per pupil, starting in 2008. He also shifted the funding formula to help schools in areas with high costs of living, especially Northern Virginia. But since then (and despite four straight years of budget surpluses), per-pupil funding has remained frozen, despite periodic attempts by lawmakers in Richmond to increase it.

The result is that Virginia chips in less for poor children to attend pre-K than does Maryland or the federal Head Start program (both of which pay $8,000 per pupil), and much less than the $9,327 per pupil that the state would pay if it were intent on providing a high-quality preschool education, according to the National Institute for Early Education Research at Rutgers University.

The state’s miserly funding makes it more difficult for some school districts to pony up the difference. As the institute’s director, W. Steven Barnett, told The Post’s Michael Alison Chandler, “The amount of money that the state is offering is too little to do this, so districts that can’t make up the difference just aren’t going to do it.”

Some sizable school systems around the state, including those in Norfolk and Newport News, have made pre-K a budget priority, ensuring that 100 percent of eligible children can attend classes. Other big systems, such as Fairfax’s and Loudoun’s, have managed to find matching money for just half of those eligible.

Prince William is in a Scrooge-ish category of its own. In addition to a shortage of funds, county officials argue that they lack classroom space, owing to rapid enrollment growth. Yet other fast-growing systems (including Loudoun’s) have done much better. The problem in Prince William is at least partly that county leaders scarcely acknowledge there is a problem. In so doing, they display contempt for the constituents they represent.