Changes to state tests, which doubled in length this year, are hitting some of the city’s neediest students twice as hard.

For students with disabilities who are given more time to complete the tests, testing can stretch as long as three hours on each day of testing. That means the students could spend more than half of the school day — and more than 18 hours total — on state exams this week and next.

At I.S. 190 in the Bronx, Maribeth Whitehouse’s self-contained special education class of eighth-graders sat down to their reading exams at 9 a.m. Tuesday. Including the time it took to hand out the test, read directions, and take breaks, her students didn’t close their test books and head to lunch until after 12:30 p.m. — at which point, one student complained, “My legs hurt.”

That was just the beginning. The schedule repeated today and will again on Thursday and next week for the state math exam.

“It’s not water-boarding, but when you’re 13 it’s pretty close to torture,” Whitehouse said of the morning stretch. “My kids would have done great if it was just three days for Book One.”

During the rest of the year, Whitehouse said, she tailors assessments to her students’ individual needs and abilities. But all students get the same state exams, administered in pretty much the same way.

“I find it disheartening that while they repeatedly tell us to differentiate, they themselves do not make allowances for that during the exam itself,” Whitehouse said about state and city education officials.

Students with disabilities receive Individualized Education Plans or 504 Plans that outline exactly how they can be assessed. Some students are entitled to modifications, meaning that their teachers would change the content of what is assessed or the threshold for proficiency. For example, a student’s IEP might dictate that if he answers 50 percent of test questions, he should be given credit for completing a test. Or a student could be given visual aids to help him comprehend assignments.

But no modifications are allowed for the state math and reading tests. The only permitted supports are “accommodations” that change the context in which the tests are given. Students whose IEPs call for accommodations might receive extra time, take the test in a separate location, or have some sections of the test read aloud.

Diane Zavala’s son, a third-grader, has high functioning autism and attends the Autism Spectrum Disorder (ASD) NEST program. His IEP entitles him to extra time on tests and to take tests in a room where the walls are wiped clean of visual stimuli that could distract him.

But after she noticed that test preparation and regular testing were triggering anxiety in her son, and after he expressed concern about the length of the state tests, Zavala initiated a change in his IEP so that he would instead receive time and a half. Even so, when she grasped just how much testing he would endure this month she couldn’t bring herself to submit him to it.

“The circumstances are bad for children with special needs,” she said. “They’re there to help him, but I think that it’s almost torture.”

Zavala joined a small cohort of parents who are opting their children out of this year’s tests. Another member of the group, Janine Sopp, said her daughter’s recent diagnosis of dyslexia would have entitled her to extra time on the tests. But Sopp decided the adjustment wouldn’t actually have any benefit.

“More time for a child who struggles with decoding is not what they need,” Sopp said. “Though it’s helpful, it could add to the frustration and definitely the exhaustion factor for a child who struggles with reading.”

Advocates say the tests simply aren’t designed in a way that makes sense for many students with special needs and that no amount of extra time can change that.