For the first time in 25 years, teachers in Denver are going out on strike.

The district has been negotiating a new contract for over a year and there was still hope they would be able to reach an agreement and avoid a work stoppage, but when the deadline passed with no agreement, over half of the teachers in Denver are calling in "sick" and picketing the school board.

Over 2,100 teachers are striking over several issues regarding pay and bonuses, especially in poverty area schools as well as high priority schools.

At odds are the bonuses paid to teachers, with teachers wanting lower bonuses but higher salaries and the district saying they are necessary because they seem to boost the performance of students.

The Denver school district says schools are going to remain open but Early Childhood Education classes will be canceled until the strike is over. Parents looking for places for their children will have a few options available until the strike is over.

Negotiations will resume Tuesday.