Rochester School Committee Chair Sharon Hartley wanted administrators to reconsider the tri-town schools’ proposed calendar, but board members said that wasn’t necessary.

On Thursday, the committee voted 4-1 to approve the 2015-16 calendar. Hartley voted against the motion.

The new calendar includes 20 hours of professional development for teachers. This year, teachers had 12 hours for professional development.

Administrators proposed half days for professional development on Oct. 27, Feb. 10, April 27 and May 8. The Joint School Committee is expected to finalize the calendar at its next meeting.

Last year, the Joint Committee reduced development hours so students would have more full days in school.

Hartley said she would have approved the calendar if those half days created an extraordinary learning experience for educators.

She said the change was worrisome.

Committee members talked about what constituted good professional practices last year, she said.

“I believe strongly in professional development,” Hartley said. “When I listened to the discussion at the Joint Committee meeting I worried that previous conversation was misunderstood.”

She said half days also inconvenience parents.

Administrators weighed their options and said this model appeared to benefit students and teachers most.

“It’s a tough balance,” Principal Derek Medeiros said. “How do we get our professionals together to better their instruction?”

Medeiros said instead of a half day, a full day could be held for students while teachers received professional development. Substitute teachers and aides would staff classrooms. However, that would hinder education.

“To have all grade levels covered would be extremely tricky,” Medeiros said. “Our [student aides] are good, but they’re not trained at the same level as our teachers. Then you would have substitutes come in, and then you have to consider the quality of the instruction.”

Medeiros told the committee that teachers treat half days with the same educational rigor as full days.

Committee member Jennifer Kulak agreed.

She said she polled her three children for their thoughts on half days.

“My fourth grader informed me that they use every single second in those half days,” she said.

Kulak said teachers needed more time to collaborate. She added the decision could be evaluated the following year.

“I think we’re building a different culture and climate in the school,” she said. “I’m in favor of half days…I want our teachers moving forward.”