On the first day of the spring Keystone exams, some Philadelphia high school students walked out while others "opted out" of the tests that soon will be required to graduate.

"It's important to fight against standardized tests," said Gian Carlos Rodriguez, 16, a sophomore at Penn Treaty High School in Fishtown, who identified himself as an organizer of the Wednesday protest. "Some people are bad test-takers."

About a dozen students showed up at Kensington High School for the Creative and Performing Arts, then left the building while the test was being administered first thing in the morning, principal Lisette Agosto said. Others didn't take the exams, submitting paperwork from parents excusing them from the tests.

"You're not forced to take a test," Agosto said.

The graduation requirement goes into effect for the Class of 2017, today's 10th graders. They must pass Algebra I, biology, and literature exams. Students are given two tries, and if they fail, they are required to complete a project-based assessment to graduate.

Walkouts were also planned at Furness and Penn Treaty High Schools, but Rodriguez said students were threatened with disciplinary action.

At Furness, no students left, but 50 to 100 who could have taken the test did not do so, principal Dan Peou said.

Rodriguez said only about five students left Penn Treaty, because administrators warned they would get in trouble. The principal could not be reached for comment.

Many parents throughout the country are fighting back against standardized tests. Critics, including many educators, say they are riddled with problems, from being too costly and time-consuming to administer to being unfair to poor districts.

"In many underfunded districts, it's an unfunded mandate, so districts aren't given any more resources to give remedial instruction," said Alison McDowell, a leader of the "opt out" movement in Philadelphia.

Pennsylvania families can opt out of standardized tests by arguing that they are opposed on religious grounds. The state Department of Education said it received 510 requests to opt out of Keystones during the spring and winter testing sessions last year.

Another problem with the tests, said Janet Torres, 18, a junior at Kensington CAPA who joined the walkout, is that students were not prepared.

She took biology last year, but her school didn't have many supplies, she said, so she decided to skip the biology test Wednesday because "I didn't really know anything about biology."

Reviews for the math test, she maintains, began two days ago.

"If they really wanted us to pass the test, they should have had things after school or during school to prepare us. . . . They know we're going to fail," she said.

Agosto said there's nothing she can do if a student doesn't want to take a test. But if students walk out of the building, that's another thing. She called the parents of the students who left.

"If the mom wants to punish, it's up to them," she said.