HARRISBURG - Eliminating music and Spanish, increasing class sizes, scaling back full-day kindergarten to half days.

That is what may lie ahead for Cook-Wissahickon School in the Roxborough section of Philadelphia if it loses an estimated total of $600,000 in funding under Gov. Corbett's budget plan.

Fear of such cuts spurred assistant principal Karen Lash to lead 180 students and teachers to the steps of the Capitol on Tuesday for an NAACP-sponsored rally.

"Eighty percent are at the grade level in math and 78 percent are reading at grade level," said Lash, noting that her own job was on the line. "We've worked very hard to make progress."

Her group was among busloads of students, teachers, and parents from across the state who arrived at the Capitol - waving signs that read "Cut Corbett Not Schools" - to demand the legislature restore $1.1 billion in education funding and deep-six a bill that would create state-funded school vouchers.

"If the Corbett budget cuts become law, the education system as most of us baby boomers understand it will end," said J. Whyatt Mondesire, president of the state conference of the NAACP. "You can't balance the budget on the backs of children and the hardest hit will be poor districts."

Mondesire said it was the first Harrisburg protest sponsored by the nation's oldest civil rights group since he took office 14 years ago.

The rally came as Corbett fights to win passage of a key plank in his campaign platform - the voucher bill. The proposal would provide tuition vouchers averaging about $9,000 to lower-income students at failing schools to allow them to attend private or parochial schools, or public schools in other districts.

It has quickly become one of the most heated and costly policy battles in the Capitol.

So far, the voucher legislation has stalled in the Senate over its cost as Republicans, who hold the majority in both chambers, negotiate with Corbett and his administration.

The voucher issue has divided education advocates and sparked a fierce and costly lobbying campaign, pitting large unions - such as the Pennsylvania State Education Association, a sponsor of Tuesday's rally - against "school choice" advocates, bankrolled by wealthy investors, who say vouchers are the answer to failing public schools.

Sen. Anthony Hardy Williams (D., Phila.), whose unsuccessful run for governor last year was largely financed by voucher supporters, drove past protesters in his Cadillac Escalade.

Williams said in a statement that while he recognizes the right of the NAACP to protest, he remains focused on passing the voucher bill. "It is tragic to condemn generation after generation to persistently failing schools simply due to their zip code or family income," he said.

Mondesire, speaking to hundreds at the rally wearing buttons with the word "vouchers" with a slash through it, stressed the link between a poor education and future incarceration. So did Donna Giddings of Philadelphia, whose mother and teenage son were shot to death in 2005.

"If you cut schools and after-school programs, what are our children to do? Where are they to go?" said Giddings, a member of the group Mothers in Charge. "Most perpetrators like the person who killed my son are dropouts. It's a vicious cycle."

Contact staff writer Amy Worden at 717-783-2584 or aworden@phillynews.com.

Inquirer staff writer Kristen Graham contributed to this article.