The president of Hawaii’s teachers union will sit down with lawmakers in a closed-door meeting today as they try to reach a compromise on implementing a law that lengthens the school day.

Teachers fear the mandate could require them to give up planning or other miscellaneous time, while the state Department of Education has warned that getting all public schools to comply with the law could cost $45 million to $55 million in next school year alone at a time when the department is facing increasingly dire budget constraints.

Legislators are looking at a variety of options for amending Act 167, which has minimums for the number of hours and days students spend in classrooms.

Among possible compromises: Minimums could be phased in through two or more years with all schools complying over time, or all secondary schools could be exempted at least for a year.

Lawmakers are confident they will be able reach an agreement before the close of the legislative session, but at a conference committee hearing yesterday said all options were still on the table.

State Sen. Jill Tokuda, chairwoman of the Senate Education Committee, said she and State Rep. Roy Takumi, chairman of the House Education Committee, will meet with Hawaii State Teachers Association President Wil Okabe today to discuss “where we go from here.”

Teachers bombarded Tokuda’s office with emails and calls last week after the union sent out an email raising concerns with the push to have schools comply with at least a portion of the instructional hours law.

The union said Tokuda had implied teachers would have to do more “without compensation.”

Tokuda said she never suggested teachers work for free, but has said that perhaps some “miscellaneous time” in a teacher’s day could be spent on instruction rather than planning, preparation or other activities.

Further complicating the issue is that instructional time for teachers is a collective-bargaining issue and must be approved by two-thirds of the teachers at each campus.

Advocates for longer school days estimate that at least 39 of the state’s 167 elementary schools meet the minimums — at least 915 hours of instruction (which averages to about five hours per day).

But only two high schools — Castle and Waianae — comply with the minimums for secondary schools, 990 hours of instruction (or about 51⁄2 hours per day), the advocates said.

Supporters of the law say schools meeting the minimums illustrate that the mandates aren’t impossible.

“We’re just pushing a national standard,” said Debbie Schatz, mother of a Kailua Intermediate School student. “Everyone else (on the mainland) is doing it.”

In general, the school day in the islands is about six hours long, which includes about an hour for lunch and recess. Students receive five to 5 1⁄2 hours of instructional time, depending on the school.

At some schools, however, students get four to 4 1⁄2 hours of instructional time.

Act 167, written in the wake of teacher furloughs last school year, was designed to make sure public school students aren’t shortchanged on the amount of time they spend in classrooms.

The first minimum hours were meant to bring the length of Hawaii school days on par with other states.

In 2013 the law calls for even higher requirements: All schools will have to increase instructional time to 1,080 hours, or six hours on average.

Takumi said he doesn’t plan to budge on one part of the law: the requirement that schools have at least 180 instructional days. (This school year, students have 178 days of school.)

But he said the instructional-hours discussion gets more fuzzy, especially since the law doesn’t define “instructional.”

Lawmakers are trying to figure out whether homeroom and even after-school activities could be considered instructional.

“What’s desirable is that all students have extended learning time,” Takumi said. “But what’s desirable and what’s possible are two different things.”

He added that lawmakers are just “going to have to be a little creative” on making at least portions of the mandate work.

Schools Superintendent Kathryn Matayoshi said of most concern is how the department will meet mandates for instructional hours as it also grapples with budget reductions for the coming fiscal biennium that could top $110 million.

The budget forecast is “pretty scary,” she said.