BOULDER, Colo. -- After two days of "sick-outs" at Boulder Valley schools, the district saw a third round of teacher strikes on Tuesday.

On Monday, 342 teachers from six Boulder Valley schools stayed home to protest a contract negotiation breakdown. On Tuesday, 269 teachers in eight different schools took the day off.

The absences are neither a "sick out" nor a "strike" because the teachers are not using their sick days and the teachers' union has not officially sanctioned the absences. The teachers who are choosing to stay home are using personal days, so they cannot be fired.

The schools impacted on Tuesday were Monarch K-8 in Louisville, Aspen Creek K-8 in Broomfield, Broomfield Heights Middle School, Anjevine Middle School in Lafayette, Birch Elementary in Broomfield, Emerald Elementary in Broomfield, Kohl Elementary in Broomfield and Whittier International Elementary in Broomfield.

Broomfield High and Manhattan Middle School teachers kicked off the protest by not reporting to work on Friday.

The teachers want a permanent one percent cost-of-living wage increase, but the district will only agree to the increase for one year, citing a negative outlook for the 2010-2011 budget. The two sides are hoping to have negotiations settled by July 1, but for now, the district is adjusting to offset the teacher absences.

Monday’s strike left district officials struggling to find enough substitutes to take the nearly 350 striking teachers' places.

"It's a lot to cover with substitutes," admitted district spokesman Briggs Gamblin.

But the district was prepared to do it again Tuesday and has 250 substitute teachers on standby in case of more sick calls. Administrators who have teaching experience will also help fill in, and some classes may be combined to deal with shortages.

Parents of Boulder Valley School District students, attending a track meet at Boulder High, said they worried that their students' schools would suffer.

"I understand the teachers' point of view but when your kids are involved it's different," said parent Debra Miller. Miller said she worried about Boulder Valley High School students in particular, who would have to have their finals administered by substitutes.

"You don't want it to happen in the last week of school, you know. These kids are counting on their teachers," said another parent, who would only identify himself as Mike.

Students worried that the sick-out would spread to their schools next.

"I think a lot of teachers are going to be missing from our school (on Tuesday)," said Angevine Middle School student Kayla Matino, who had been hearing rumors all day about sick calls at her school.

"That wouldn't be so good because I have a final ... in science," said Louisville Middle School student Kaylin Ronacher.

But district officials said finals week may wind up being the best time for the strike.

"In many ways proctoring a test is the easiest kind of classroom coverage to provide," said Gamblin.