Public schools, protected from previous rounds of budget cuts, may have to tighten their belts this time.

The proposal unveiled by the governor's budget office Tuesday slashes $125.6 million from the amount schools were scheduled to receive for the 2009-10 school year.

School funding is protected under Amendment 23, passed by voters in 2000. But legislators over the years have added amounts above the level required by the amendment.

The state saves more than $70 million by rolling back one such discretionary expenditure - a cost-of-living factor - to levels in effect for the 2000-01 school year.

"We think this is allowed" under the amendment, said budget director Todd Saliman.

Losing the largest amounts of money would be Jefferson County and Denver, each with cuts of $7 million or more.

The cuts are not proportional to enrollment, but are based on a formula used to distribute the cost-of-living increases. For example, Cherry Creek School District takes a disproportionate hit compared with the much larger Jefferson County.

Jane Urschel, associate director of the Colorado Association of School Boards, said the cuts could affect classrooms or lead to teacher layoffs in some districts.

"It looks like it would come to that," Urschel said.

Jefferson and Douglas counties are already making budget cuts after losing tax- increase proposals at the polls in November, she said.

Urschel said the districts already were bracing for cuts as the economy soured.

"We're all kind of in a trance - people are just waiting to understand how bad it is going to get," she said.

Colorado could see more than $400 million in school funding as part of the federal economic stimulus package. But Saliman and several lawmakers said they're not counting on that money, some of which may be earmarked for specific programs rather than for general classrooms.

Districts that will feel pinch

Metro-area school districts taking the biggest hits under proposed state budget cuts:

* Denver: $7.2 million

* Jefferson County: $7.0 million

* Douglas County: $4.9 million

* Cherry Creek: $4.3 million

* Northglenn-Thornton: $3.2 million

* Aurora: $2.9 million

* Boulder: $2.6 million

* St. Vrain: $2.2 million