What Substitute Teacher Shortages Teach Us About On-Call Labor

A School District's Morning Problem

Every school day begins with a small logistical gamble. Some number of teachers will call in sick, take personal leave, or attend training, and the district needs a warm body in each of those classrooms by first period. There is no ramp-up time, no negotiation window, no ability to push the start date. The class either has coverage or it doesn't.

That single constraint, needing to fill a shift on a few hours' notice with someone who wasn't scheduled to work that day, is what makes substitute teaching a useful lens for thinking about contingent labor generally. Districts have been wrestling with sub shortages for years, and the fixes they've tried, and the ones that haven't worked, map onto almost any business that leans on an on-call pool: home health aides, event staff, warehouse temps, freelance drivers, per diem nurses.

Why Contingent Pay Structures Break Differently Than Full-Time Pay

A full-time employee's compensation is built around predictability. They know their hours, their benefits, and roughly what a raise cycle looks like. A substitute's pay is built around uncertainty on both sides. The worker doesn't know how many days they'll get called in a given month, and the district doesn't know whether today's rate is enough to make someone say yes to a 6 a.m. text.

This is where contingent pay tends to underperform even when it looks reasonable on paper. A day rate that seemed adequate five years ago erodes against inflation and against the opportunity cost of gig work, tutoring, or retail jobs that offer steadier hours. Research compiled by the National Council on Teacher Quality shows that districts that raised substitute pay rates saw measurable improvement in fill rates, and that the districts struggling most were often paying substitutes a rate that hadn't moved in years while full-time teacher salaries continued to climb.

The lesson generalizes cleanly: if the contingent rate stagnates while the market for people's time moves, the pool doesn't shrink gradually. It collapses at a threshold, because the marginal sub who was on the fence about taking assignments simply stops answering the phone.

The Last-Minute Fill Rate Problem

Full-time staffing failures show up as vacancies. Contingent staffing failures show up as fill rate, the percentage of open shifts that actually get covered, and it's a much more volatile number. A district might fill 95 percent of absences on a normal week and 70 percent during flu season or the week before a holiday, when demand spikes and the substitute pool is drawing from the same limited group of available people.

Research summarized by Harvard's Journalist's Resource points to a consistent pattern: fill rates drop hardest exactly when coverage matters most, because absence rates among full-time staff and substitute availability move in opposite directions during peak illness periods and around holidays. The people most likely to say yes to a last-minute shift are also the ones most likely to be unavailable when everyone else needs coverage too.

Any business running an on-call model should expect the same seasonality. A home services company that relies on subcontractors for overflow jobs will see the same crunch during storm season. A hospital's per diem nursing pool thins out during the exact weeks when full-time nurses are calling in sick. The fill rate isn't a single number to track, it's a curve that needs to be modeled against known demand spikes, not treated as a flat average.

Building a Reliable Pool Without Full-Time Costs

Districts that have improved their substitute reliability generally didn't rely on pay alone. The NCTQ's comparative work on pay policy alongside non-pay tactics for stabilizing substitute pools found that simplified onboarding, faster background check turnaround, and basic logistical support (like giving subs lesson plans and classroom context ahead of time) made a measurable difference in whether people accepted repeat assignments.

This matters because contingent workers weigh friction differently than full-time employees do. A new full-time hire will tolerate a clunky first week of paperwork because the job is worth the investment. A substitute deciding whether to take tomorrow's assignment is making a much smaller bet, and a bad first experience, an unclear classroom, no lesson plan, a confusing check-in process, is often enough to make them decline the next call. Reducing onboarding friction isn't a nice-to-have for contingent labor. It's closer to a conversion rate problem: every point of friction removed increases the odds that a marginal worker takes the next shift instead of ignoring it.

The same logic applies outside education. A staffing agency placing warehouse temps sees higher no-show rates when the check-in process at the client site is confusing or the shift instructions arrive late. A firm building an on-call bench of contractors, the kind of problem explored in how contracting businesses hire field technicians when the applicant pool is too small, runs into a version of the same issue: reliability comes less from the pay rate alone and more from how easy the organization makes it to say yes repeatedly.

The Morale Problem Full-Time Managers Miss

There's a subtler issue underneath pay and fill rates: contingent workers rarely get the informal relationship-building that keeps full-time staff engaged. A substitute who floats between five different schools doesn't build the same rapport with a principal that a full-time teacher does with a department head. That absence of belonging is a real driver of attrition from the pool, separate from pay entirely.

The parallel to shift-based full-time work is closer than it might seem. Contingent scheduling problems and shift-culture problems are cousins, not opposites, and the same organizational blind spot shows up in hospitals that treat scheduling software as a fix for a broken shift culture rather than addressing why staff dread certain shifts in the first place. A better app doesn't solve a culture problem. Neither does a slightly higher day rate, on its own, solve a belonging problem.

Organizations that depend on contingent labor pools tend to treat the arrangement as purely transactional: post the shift, offer the rate, hope someone bites. The federal government's own framing of contingent and on-call work as a distinct labor category underscores that this isn't a niche scheduling quirk, it's a defined segment of the workforce with its own economics. Treating it that way, rather than as a diluted version of full-time staffing, is usually the first step toward fixing it.

What This Means for Any On-Call Workforce

A business that depends on contingent labor should ask three questions before assuming a shortage is a pay problem alone: Is the rate keeping pace with what comparable work pays elsewhere? Is the onboarding and shift-preparation process removing friction or adding it? And is there any relationship built between the organization and its contingent workers, or does every shift start from zero?

Substitute teaching makes these questions visible because schools can't quietly absorb an unfilled shift the way an office might absorb an empty desk for a day. But the underlying mechanics, pay that erodes relative to alternatives, fill rates that collapse exactly when demand peaks, and friction that quietly drives away marginal workers, apply just as much to any business running on a bench of people who can say no.