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WESTMINSTER, Colo. -- Standley Lake and Conifer high schools canceled classes Friday because of several teacher absences, the Jefferson County School District said.

Some called in sick, others took vacation. It was no secret there were plans for an organized action. Teachers and the school board have had a disagreement over a couple of issues.

"I apologize for anybody who was inconvenienced but I also recognize that our responsibility is making sure kids are safe and secure," superintendent Dan McMinimee said.

One of them is a new teacher pay model that the school board voted to approve Thursday night.

Under the new teacher pay model, the starting teacher's salary would go up about $5,000 a year, but raises will be determined based on performance. Teachers rated as ineffective or partially effective would receive only a one percent raise or the possibility of no raise at all.

"We want to make sure that all of our effective and highly effective teachers get good compensation increases this year, after having no raises for while. I was delighted with that outcome and that final compensation plan and very disappointed this morning to see that some of our teachers chose not to show up to work at two of our schools." says school board president Ken Witt.

The other issue has to do with reviewing the AP U.S. History curriculum. The board did not take action on that issue and will take it up again in a couple of weeks.

Dozens of students Friday morning and again in the afternoon stood outside Standley Lake High School in a protest opposing the board's plan to review AP History. The board has expressed concern that it's too negative or "un-American."

The students say they would've protested even if classes had not been canceled. "It was kind of sad because we wanted to stand up out of class and walk out and I think that could have made a bigger impact, but it was also cool because we got to see what our teachers can do."

Conservatives across the country have been pushing back against new guidelines for AP U.S. history classes, accusing the college board, which is behind Advanced Placement courses, of revisionist history and anti-American bias. In response, a conservative member of the Jeffco school board wants to create a new, board-appointed committee for curriculum review.

There’s no denying the Advanced Placement U.S. history course at Wheat Ridge High School is slightly different this year.

"How we teach it has changed,” Wheat Ridge history teacher Stephanie Rossi said.

The new AP framework developed by the College Board over the past several years allows Rossi to spend less time emphasizing memorization for the final AP exam.

"I'm really excited about it because we can dig deep into some topics,” Rossi said.

But conservative critics, including the Republican National Committee, argue those topics focus on the negative aspects of our history, amounting to a class that’s anti-American.

"I've heard that criticism, but I haven't seen evidence of that in the books that I'm using,” Rossi said. “It's still the same story, it's still the same information.”

The Colorado Board of Education can’t direct curriculum for local districts, but on Wednesday the Texas Board of Education did, voting against following the AP framework in it’s classrooms.

Conservative JeffCo board member Julie Williams used language from the Texas board to push for a new committee for curriculum review in JeffCo. The committee would follow the following criteria: “Materials should not encourage or condone civil disorder, social strife or disregard of the law. Instructional materials should present positive aspects of the United States and its heritage.”

After outrage from many parents and teachers, a fellow board member removed that language from the proposal Thursday. The new proposal will likely be voted on in two weeks.

Still, many in attendance said they remained concerned about the potential for censorship.

"I don't know what I would say at this point in time, besides you should visit the classrooms to find out what people are really doing,” Rossi said. “Don't make assumptions that they are going to teach students to not like America. I'm kind of insulted by that."​

Superintendent Dan McMinimee said 32 teachers at Standley Lake and 18 at Connifer called out sick, and while the overall number of sickouts district-wide was on average, he said because of the shortage of teachers at the two high schools it was best to cancel classes as a safety precaution.

The Jefferson County Education Association released a statement late Friday morning: "The Jefferson County Education Association is aware of the situation at Standley Lake High School and Conifer High School. This was not organized by JCEA but we certainly understand the frustration teachers and the entire community are experiencing when their elected officials are making decisions in secret, wasting taxpayer dollars, and disrespecting the community's goals for their students. Last night’s discussion about censoring the AP History curriculum is yet another example of this board majority shortchanging our students."

The question now is what will teachers do on Monday?

"For me, it's less about punishment and more about understanding and trying to pick up the pieces and move forward," McMinimee said.