(CNN) It's national Teacher Appreciation Week , but you wouldn't know that by talking to teachers in Oregon.

Tens of thousands of frustrated teachers were airing their grievances at protests across the state Wednesday. But unlike with other teacher walkouts , these educators aren't fighting for higher raises.

They're fed up with overcrowded classrooms and a lack of support staff, including school nurses and mental health counselors.

"Nearly 45% of all reported classes in Oregon have 26 students or more," said John Larson, a high school English teacher and president of the Oregon Education Association

Some classes have 56 or more students, he said.

So instead of going to class, many teachers were taking unpaid days off work to flood at least six protest sites across the state

The mass exodus of teachers has already forced 25 school districts to close 600 schools Wednesday, Larson said.

The biggest district to close, Portland Public Schools, has more than 46,000 students.

"This is historic," Larson told a sea of red-shirted teachers, parents and students at a riverfront rally in downtown Portland. "This is what we came here for today -- is to make sure that we fund our schools."

Participants carried signs with messages such as "Class size matters" and "Teachers just wanna have fund$."

Speakers lamented overcrowded classrooms, schools with no guidance counselors, and the reliance on outdated computer equipment.

Later Wednesday, hundreds of teachers and supporters marched to the state Capitol building in Salem for a massive rally.

What do teachers want?

It's not just funding for smaller class sizes. Union members also want:

that national experts suggest. And the shortage of mental health counselors is a big concern across the country -- especially after all the recent school shootings. -- More school counselors. Oregon has half the school counselors that national experts suggest. And the shortage of mental health counselors is a big concern across the country -- especially after all the recent school shootings.

-- More school librarians. Currently, there are only 158 school librarians in Oregon -- less than one librarian per district.

-- More school nurses. There's only one nurse for every 5,481 students. That's four times less than national recommendations, the OEA said.

-- A restoration of art, music and physical education programs that have been cut by budget constraints.

-- More funding for school supplies. The OEA said 94% of teachers spend their own money on classroom supplies "to make up the difference between what their students need and what districts can provide."

-- The passage of state House Bill 3427, dubbed the "Student Success Act." The bill would increase funding for K-12 education by 18%.

What are politicians saying?

State Sen. Rob Wagner, chair of the Senate Education Committee, says he hopes colleagues will pass the Student Success Act.

"The Student Success Act specifically raises revenue for schools, offering targeted investment grants for more mental health support, more after-school programs and much more," Wagner said.

"It adds $1 billion a year for schools in Oregon, with districts able to figure out where they need the money most. This is a once in a generation investment for our children."

If the bill passes the legislature, Gov. Kate Brown is ready to sign it into law, her office said.

"The Governor is supportive of Oregon educators who are rallying Wednesday," Brown's office said in a statement.

"Her budget proposal included funding to reduce class sizes, help teachers address mental health and behavioral issues that students face, and continue to expand career-connected learning opportunities for students."

Brown on Wednesday afternoon tweeted, "I stand with Oregon's teachers today," listing some changes expected to come with her proposed budget.

But the union says it's not backing down until schools are guaranteed more resources for students.

"We're putting pressure on lawmakers they haven't seen from us before," Larson said.

Why are so many teachers protesting these days?

Last week, thousands of teachers in North and South Carolina swarmed their state capitols, demanding more mental health counselors , higher pay and more money for support staff.

Union leaders say much of the nationwide anger stems from states slashing education budgets during the recession a decade ago. But despite the improved economy, many education budgets have not caught up -- especially when considering inflation.

So what will happen in Oregon if teachers' demands aren't met?

"There are no longer-term walkouts currently planned," Larson said, "but Oregon educators will do whatever it takes to make sure our schools can afford what students need."