Lucia and Ignacia Barajas are sisters who attend Compton High School in southern Los Angeles County. They want an education, but their school seems unable to give them enough time to get one.

During the 2011-2012 school year, Lucia’s biology teacher went on maternity leave. For two months there were nothing but short-term substitutes in the class, most staying only a few days. In the fall 2013 semester, Ignacia’s American history class had more than 10 substitute teachers, and some days none at all. The restless students waited outside the door until they were sent to the library or another classroom.

Wasting time is common in the nation’s low-income schools. Class schedules can be a mess at the beginning of the year, forcing students to wait days in the library for their assignments. Lockdowns because of neighborhood violence detract from learning time. Teacher absence rates are high, and instructors will often quit mid-year with no good replacements available.

A little-known time-waster is something called inside work experience (IWE) or service learning. I first encountered it 30 years ago while doing a book about an inner-city school. If the right class wasn’t available or expectations for the student were low, he or she would be assigned to do chores for a teacher during that period. It’s still happening.

At Fremont High School in the Los Angeles city school district, Eric Flood recently had an IWE period during which he sorted mail, ran errands and socialized. Fremont student Edith Quintero had two such periods during which she made copies, entered attendance data into a computer and chatted with friends.

I know this because of a remarkable lawsuit just filed by, among others, the ACLU Foundation of Southern California and the Public Counsel Law Center against the state of California on behalf of 18 students at seven schools. The class-action complaint says students are not receiving the equitable education the state constitution requires.

Inequitable education class actions are not new. For decades, many states have been sued for not giving low-income children the opportunities provided in affluent communities. But this suit is different. Previous class actions focused on inadequate funds, teacher quality, facilities and materials, such as textbooks. This suit is about insufficient and inequitable time for learning. Stanford University economist Eric Hanushek, who chronicled unequal education suits in his book “Schoolhouses, Courthouses, and Statehouses,” said this complaint is “something new” that focuses on “what the students are getting in the classroom.”

In a recent column, I noted a National Center on Time and Learning report on how much more high-achieving schools with longer school days and years offer their students. In those schools, teachers have more time to plan their lessons and confer with other teachers. At the schools named in the California lawsuit, it is a struggle just to get time in a classroom every day with a competent instructor.

“The effects of learning time lost in these seven schools are not isolated or linear,” the suit said, “but cumulative, compounding and self-amplifying.” State standards, like the new Common Core, “are predicated on a carefully prescribed sequence of teaching and student mastery of academic content,” it said, but “as the loss of learning time accumulates, the gaps grow between the base of knowledge and the skills reasonably expected of students and what they have been able to acquire.”

For Mark Rosenbaum, chief counsel of the ACLU of Southern California, this is one more in a series of suits that have forced the improvement of facilities and increased access to challenging courses. New research shows what longer days can do for disadvantaged students. What we need is more attention to bad schedules, lack of support for teachers, credit for busy work and the many other ways our schools waste time.