Crises in Pennsylvania public education aren’t difficult to find these days, but if you’re searching for an often-overlooked problem, look no further than the men and women who take over when students’ everyday teachers are not in the classroom.

Substitute teachers are a vital part of school districts across the country, and the simple fact is there aren’t enough of them to go around these days — in Western Pennsylvania or many other places.

School administrators around Butler County point out that the problem isn’t just local.

Superintendent Tracy Vitale of Seneca Valley says the problem is statewide. Seneca Valley bumped up the district’s pay rate for subs last week and asked parents to consider getting certified.

The Pennsylvania Department of Education certified 5,000 substitute teachers last spring, Vitale said. State officials in a normal year certify more than 15,000.

The shortage inevitably means that some absent teachers’ positions can’t be filled each day. Dale Lumley, the superintendent of Butler School District, said it’s not unusual for two to four positions to go unfilled each day at the district. That puts pressure on other teachers and administrators to step in and fill the gaps.

By all indications, Pennsylvania school districts aren’t alone in this problem, or in casting about in any and every direction in an attempt to mitigate it.

At the Colorado school district of Boulder Valley, school administrators are so desperate that two weeks ago they opened the substitute teacher pool to those without a bachelor’s degree.

In West Virginia, lawmakers voted in 2013 to require districts’ central office administrators to do three days of substitute “fill-in” duty each year, citing a substitute shortage.

And school districts across the country continue to report falling levels of success at filling the positions of absent teachers.

That goes to show just how complex and frustrating the problem is for school districts. Business managers say they don’t have a clear idea of why the shortage is occurring, though they suspect pay rates and inconsistent work schedules play a part.

Administrators say rule changes to Pennsylvania’s teacher retirement system, PSERS, are also a factor. Where in the past retired teachers often returned as substitutes, Lumley said, now the state frowns on such arrangements and places limits on the number of days retirees can substitute.

The solution to this problem may not yet be apparent, but the first step in confronting it couldn’t be more clear. We have to acknowledge its scope, size and potential impact on students and school systems across Pennsylvania.

Once that’s done, the real work of teasing out a solution to this slow-burning crisis can begin.