SIOUX CITY | While the Iowa Legislature battles over when the 2015-16 school year will begin, what often gets overlooked is how the year is counted once started.

A big shift occurred this year, as an overwhelming number of Iowa school districts moved to count their yearly instructional time with students in hours instead of the longstanding method of 180 days.

After a sea change in the counting mechanism due to a new Iowa law, the 2014-15 year is the first in which school districts had the option of counting by hours rather than days. The threshold is 1,080 hours, which equates to an average of six hours per day, or 180 days.

School districts had to tell the Iowa Department of Education which counting method they chose. According to department statistics, 39 out of 338 districts, or 11.5 percent, are using the 180 days method this year.

Looking at Northwest Iowa districts alone, the percentage counting by hours instead of days is 89 percent, or 40 out of 45 districts.

Moving to an hours-based calendar allows districts additional flexibility. If, for example, a school day ends early because of poor weather, the hours students were taught may be counted on an hours-based calendar. On a days-based calendar, any school day that does not reach six hours is not counted.

Time students use to eat lunch is not included in the instructional hours count.

The Sioux City School District is on the new hours method. The five Siouxland districts that still count by days are Denison, South Central Calhoun, Hartley-Melvin-Sanborn, Harris-Lake Park and Estherville-Lincoln Central.

Proponents said the switch would give local school boards more say over how to design a school year that's best for their students. Coincidentally, the ongoing battle over the school start date could prevent local decisions on whether the beginning comes earlier or later in August.

Harris-Lake Park Superintendent Dennis Peters said that's a mixed message on the value of local decision making. "We like the local control of the start date, because we like to finish our semester by Christmas," he said.

The latest discussions have involved whether Aug. 23 will be mandated as the earliest starting date.

As for the hours/days calendar bill, the state's top education lobbying groups — the Iowa Association of School Boards, Iowa State Education Association, the School Administrators of Iowa, Professional Educators of Iowa and the Iowa Catholic Conference — were either for it or neutral.

Iowa Department of Education spokeswoman Nicole Proesch said "hours is probably the most flexible" method. Proesch said schools can always go over the minimum hours of instruction, which will happen in some districts.

Sioux Center (Hawarden) School District Superintendent Patrick O'Donnell said the district had 819 hours of instruction through Wednesday, and is on track for 1,102 hours, by the final day in May. That would be 22 hours above the minimum required.

Said O'Donnell, "Whether it is hours or days, it is all about instructional time and we don't waste instructional time."

Peters said Harris-Lake Park stayed with the school days measurement for this year, in part because teacher employment contracts are specified by days. But he said H-LP will join the trend to hours counting in 2015-16, a change he's recommending that the School Board adopt in April.

Peters said flexibility is key, so in an hours-based calendar, districts could elect to have slightly longer instructional days if needed to make up for canceled school snow days.

When the change was being hammered out legislatively in 2013, Sioux City School Board President Mike Krysl supported the hourly proposal, saying the district's calendar already exceeded the 1,080-hour benchmark.

Sioux City Community Schools Human Resources Department Director Rita Vanatta said change has been fine. Sioux City is on track to have instruction for 1,118 hours.

"The hours calendar has worked in its first year of implementation," Vanatta said.