TAMPA — A protest over teacher pay that began with some 15 students early this week mushroomed into much larger movement Wednesday as hundreds of Hillsborough County high school students from eight campuses briefly walked out of their classes.

Students at Alonso, Armwood, Freedom, Jefferson, Middleton, Robinson and Sickles high schools filtered out of classrooms and gathered outside their respective buildings, district officials said. Leto High students released a video indicating they held a demonstration too. Many were clad in black in a show of solidarity. Some held signs that said, "Dig deeper, pay my teacher," and, "Praise the raise."

The groups at each school ranged from about 20 to several hundred.

The students remained on campus and most went back to class about 15 minutes later, said district spokeswoman Tanya Arja. Armwood was the only school considering disciplinary action, she said.

Strawberry Crest students walk out to protest teacher pay

Hillsborough teachers get a hard no on scheduled pay raises

Destini Washington, 18, wasn't sure how many of her fellow students would follow her outside in an organized skipping of second period at Jefferson High.

Just days earlier during an honor society meeting, she urged her classmates to "forget senior prank" and join her in protesting what she described as a broken promise to teachers. About 200 students heeded her call.

"I didn't know what was going to happen when we got out there," said Washington, the head of her student government association whose mother teaches history at Jefferson. "But it was better than I expected."

At Middleton High, 17-year-old senior Rebecca Gaschler said she first heard about the walkout idea from a Jefferson student on Snapchat, where it spread to other Middleton students and grew into a text message group of about 100 people.

Wednesday morning, students tried to leave the building between first and second periods "but the school resource officers were adamant about us getting back to class," Gaschler said. Then principal Kim Moore came onto the school PA system, she said.

Moore mentioned walkouts were happening at other schools and acknowledged the students' rights to demonstrate and respected their message, Gaschler said. But the principal had a request.

"She said since we're doing this for the teachers, respect the fact that they're here to teach us," Gaschler said.

After the announcement, between the break between second and third period, dozens of students filed out of the building and gathered at the flagpole. They stood there for about 10 minutes, and then returned to class.

Moore could not be reached for comment Wednesday.

The demonstrations came a day after about 15 students walked out of class at Strawberry Crest High for the same cause. Administrators disciplined several of them with a day of in-school suspension.

Tensions in the district started brewing late last month when teachers were told they were not getting the raise that school leaders said they'd receive if they proved they were effective under a three-year evaluation system.

The underlying financial issues trace back to the summer of 2015, when superintendent Jeff Eakins, who was new on the job, learned the district was losing tens of millions of dollars each year in its main reserve account.

He quickly identified the teachers' new pay plan as the chief culprit. Salaries and performance bonuses jumped by a combined $77 million, forcing the district to tap into its reserves to make the last month's payroll and produce a balanced budget.

Since then, uncertainty has surrounded the pay plan, which gives teachers a $4,000 increase every three years if they get high enough evaluation scores.

The district honored the plan in 2015 and 2016, although its budget officer estimated that doing so cost $17 million each year. Along the way, the district cut spending on busing and materials and shored up reserves by transferring money in and out of various funds and accounts.

This year is different, Eakins says. The district is running out of places from which to transfer money. Two out of three bond rating firms have issued negative outlooks, meaning the district is in danger of seeing its credit rating drop. Should that happen, it would be more expensive to borrow money needed to build schools in the high-growth suburbs.

On the other side, teachers say the pay plan is part of a bargain they made when teaching reforms were implemented in 2010 under a partnership with the Bill & Melinda Gates Foundation. In agreeing to sign up for the new plan, the teachers gave up some rights and extra compensation for advanced degrees. While the information sheet they were given states that the district can revisit pay rates when money is tight, union leaders argue that the district still spends money on executive salaries and in other ways.

Teachers appreciate the students' show of support but the union does not want them to disrupt the school day and has not encouraged them to take do anything that would expose them to disciplinary action, teachers union executive director Stephanie Baxter-Jenkins, said in an interview on the Tampa Bay Times Gradebook podcast.

"We certainly are for general activism," Baxter-Jenkins said. "I just think there are ways kids can do it without leaving school, without interrupting the school day. But again, these are kids taking on something they see as wrong and trying to do something about it, and so from the perspective of a parent, I can also say that there's a piece of me that really likes that we have young people that think they can make a change in the world."

Meanwhile, emails are going out to the School Board, Eakins and the media. Teachers have picketed outside Steinbrenner High, and are encouraging one another to "work the contract," meaning only when school is in session.

Gaschler, the Middleton student, said she and her peers were glad they could send a message with minimal disruption to the school day, but their action isn't ending there.

They have plans for a similar demonstration next week and plan to attend the School Board meeting. They'll point out that students like Gaschler, who plays trombone in the band, get shortchanged if teachers don't stay after school to help with clubs and activities.

"They need to figure out the budget issue," she said, "because it's not fair to teachers and it's not fair to us."

Times Staff Writer Marlene Sokol contributed to this report. Contact Tony Marrero at tmarrero@tampabay.com or (813) 226-3374. Follow @tmarrerotimes.