Fairfax County School Superintendent Karen Garza is proposing significant changes to the school calendar for next fall, a move that would eliminate early elementary school release on Mondays and would effectively add 10 days to the schedule to account for inclement weather.

The plan would change how the Fairfax school system counts annual instructional time, shifting from a 180-day school year to a 990-hour school year, each an option under Virginia rules. Fairfax currently works with a 183-day schedule, building in a three-day cushion for weather. By shifting to an hourly count, the schools would be able to absorb 13 snow days in a school year without having to alter their schedules because students would be in school for far more than 990 instructional hours.

The model would be similar to Loudoun County’s. This year, Loudoun did not have to change its schedule because of frequent snow because it follows the hourly count and has as many as 15 extra days built into its schedule.

School officials said the Fairfax plan, which could go into effect as soon as September, would carve out more time for teachers to prepare for classes and would provide students with more time in the classroom. It also would eliminate half-day Mondays from the elementary schedule, which has vexed families with young children for decades by creating complex day-care situations.

Middle school and high school students would see no change in their schedules, but the snow day flexibility likely would mean a more predictable end-of-year schedule in the event of snow. The schools had 11 snow days this past winter, causing the system to extend the school year by three days. School officials said snow days averaged about four per year during the past three decades, but there have been three years with 11 snow days — 2003, 2010 and 2014. In those years, schools had to scramble to fill instructional time.

“I believe this change is necessary because it is the solution to address the long standing need to increase the amount of self-directed planning time for our elementary teachers,” Garza said in a statement to The Washington Post. “It also addresses the calendar problems that we encountered this year which forced us to extend the school year until June 25. I am mindful of the challenges we will face should we determine it is best to move forward with the change for this coming September.”

The current half-day Monday schedule for elementary schools has been in place since the 1970s, school officials said. The new schedule could provide more continuity for parents, teachers and students but also could cost the school system between $4 million and $7.6 million, a significant new expense proposed immediately after the School Board and schools officials spent months locked in a budget battle with the board of supervisors, claiming a looming “crisis” that didn’t materialize.

School Board Chairman Ilryong Moon (At Large) said he supports Garza’s plan, adding that the funding could be found in money that is expected to be left over from the current fiscal year budget. The schools frequently end the year with millions of dollars in extra cash.

“This is an issue that the community has been concerned about for a long, long time,” Moon said.

Some supervisors questioned how the School Board could so easily come up with the funding for the new schedule’s costs — most of which would go to paying teachers for the additional 21 / 2 hours of classroom time per week — after school leaders claimed a dire funding situation.

Supervisor John C. Cook (Braddock) said the schools could add to their fiscal woes next year by using the leftover money to fund the adjustments for the new calendar. The school system often uses some of the leftover money to help balance the following year’s budget.

“It’s going to cause a greater deficit in the next year,” Cook said.

Jeff C. McKay, supervisor for the Lee district, said he supports the plan but noted that the schools have more flexibility in the budget than they let on earlier in the year.

“It’s a matter of what your priorities are,” McKay said. “Every year, they have a questionably large beginning balance. I guess what that says to me is next year we may have the same challenges as we had this year.”

Steven Greenburg, president of the Fairfax County Federation of Teachers, said he backs Garza’s proposal, which he believes would benefit teachers and students.

“The kids would be in school for longer, and that will help address the achievement-gap problem,” Greenburg said.

School Board member Elizabeth Schultz (Springfield) said the new calendar will help the administration solve multiple problems in one move: snow days, teacher planning time and the achievement gap. She also said school officials think the new calendar will save the system money each year because the schedule will allow the schools to be more efficient.

“Here’s an issue that presents the opportunity to improve the situation across the board for parents, students and teachers,” Schultz said.

Other School Board members said the plan seems rushed and costly.

Kathy L. Smith (Sully) said she is in favor of the new calendar but wanted to wait to implement the plan until 2015.

“If we feel like we need more time to do it right, then we should take more time to do it right,” Smith said. “I personally don’t believe we can accomplish it the right way this year.”

Vice chair Tammy Derenak Kaufax (Lee) said the new calendar would be costly for the school system: “It’s a great opportunity for our students, but exactly where is that going to come from?”

School Board member Daniel G. Storck (Mount Vernon) said implementing the new calendar by September would be a “heavy lift.”

“I’m open to it,” Storck said. “But we have some significant work to do.”