After Hurricane Irma kept Florida children out of classes for a week of September or longer, school district officials had a math problem to solve.
If primary students had to receive at least 720 hours of classroom instruction over the year, and secondary students 900 hours, how much time would they need to make up?
Some districts, including Pinellas County, added full days back into their schedules for all schools to ensure they met state mandates. Others, including Hillsborough County, eliminated early release days to return time to their calendars.
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A third group, which included Pasco and Hernando counties, went more granular.
Instead of adding days or hours, they looked for minutes available in each school's schedule. And they found that while some campuses needed more time to get back up to the state minimum, others had enough remaining to get by without any changes.
That scenario raised Pasco superintendent Kurt Browning's eyebrows.
"It should never happen, to have 11 schools out of 90 that have that much variability," Browning said.
The hurricane has highlighted a little-known fact about the way educators routinely budget valuable learning time. While schools must meet minimum guidelines, campuses are allowed to set their own daily schedules, a system that gives them flexibility but also results in significant differences in learning time over the year.
One school can end the year with several more days' worth of learning time than another, when all those minutes are accounted for.
In north Pinellas, for example, Dunedin and East Lake high schools each offer seven courses a day with a 30-minute lunch. But they differ in the amount of time they allow for students to change classrooms, what schools call "passing" time.
Dunedin's courses last 47 minutes with five minutes for passing, while East Lake's run 46 minutes with six minutes between them. So each day, Dunedin students get seven minutes more of instruction. Over 180 days in a school year, that comes to 1,260 minutes, or 21 hours more than East Lake.
The bottom line: Dunedin students receive the equivalent of 27 more classes than their peers at East Lake over the year — or about five days worth of school.
Another way to see the variation among schools is to look at what happened when Pasco officials studied campus schedules to find where they could make up hurricane days. They found that Pasco High and Rushe Middle wound up eight minutes short per day. Sunlake and Mitchell high schools needed two minutes daily. Hudson Middle had to add back one minute a day to meet the mark.
"The perception parents have is one of no consistency," Browning said. "There is no common thread between schools that got the extra minutes. That is problematic to me."
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Individually, the stray minutes across a school schedule might not seem like much to worry about.
"I think the pace of instruction is dictated by the material to be taught, and I doubt the minute will have much effect on a teacher's goals for a lesson," said Duke University interim dean of social services Harris Cooper, who still supported making school schedules more uniform.
"But that's a lot of time for a kid," argues Michelle Valladares, associate director of the National Education Policy Center at the University of Colorado. "Minutes of the day is an indicator of what is going on in the schools. Inequity in time can indicate inequity in other areas."
A printed bell schedule represents only part of what goes on during a school day. Things like school lockdowns, teacher absences and test preparations can further cut into learning time, Valladares explained.
"There is a whole other level of not getting instructional time," she said, pointing to research on the topic from Harvard, the Annenberg Institute and Ford Foundation for support.
Kids in some schools "are getting less," she said. "And the time they are getting in school is used less well."
Pinellas County associate superintendent Kevin Hendrick acknowledged the importance of teaching time as key to learning.
The district, like most others, builds time beyond the state minimum into every school's master schedule, he said. Some schools that have struggled with student performance get an extra hour beyond that.
"In general, more instructional minutes can be correlated to achievement," Hendrick said.
He added, though, that because of schools' different needs, "variation of minutes within the student day is expected."
But such fluctuation can be seen even among the schools with the longer days. Boca Ciega High's block schedule shows four 91-minute courses per day, for instance, while Lakewood High's includes four 95-minute courses.
That comes out to a difference of 16 minutes of daily lessons between the two south Pinellas schools, or 2,880 minutes — 48 hours — over the school year. Put another way, Lakewood students get about eight days' worth of learning time more than their Boca Ciega peers across the year.
The question becomes, how much variation is acceptable?
It's an issue that Pasco County district leaders plan to tackle. Browning said he expected to have more clear and equitable schedules in the coming year.
Though pleased the administration found a way to make up lost minutes without taking away families' planned vacation time, School Board members expressed dismay after learning not all schools were providing the same teaching time.
The notion that longer lunches — by as much as 20 minutes a day — might be a culprit did not sit well with everyone.
"I like to see the most instructional time we can provide," said board member Colleen Beaudoin, also a teacher and parent.
Pasco assistant superintendent Kevin Shibley noted that some schools had less teaching time because they held homeroom, study hall or remediation assistance. The district views such activities as critical, he said, but they don't count toward the state minimum.
Schools often can find extra time within their existing schedules, said Valladares, of National Education Policy Center. What's important is to make sure it's used well.
"A lot can happen in a classroom in five minutes," she said. But "more time is not always better time."
She encouraged all districts to take a closer look at how they use their class days.
"What you're seeing," she said, "is just the tip of the iceberg."
Contact Jeffrey S. Solochek at email@example.com. Follow @jeffsolochek.