High-poverty schools have so much trouble hiring and retaining teachers that students may be taught by a rotating cast of substitutes, reports Emma Brown in the Washington Post. There’s no guarantee the sub will know the subject they’re supposed to be teaching.

Mya Alford dreams of studying chemical engineering in college, but the high school junior is at a disadvantage: Last year, her chemistry teacher at Pittsburgh’s Westinghouse Academy quit just weeks after school started, and the class was taught by a substitute who, as Alford put it, “didn’t know chemistry.”

The year before, there was no permanent biology teacher until December. Students at Westinghouse, a high-poverty school in one of Pittsburgh’s roughest neighborhoods, often see a rotating cast of substitutes, Alford said.

Teaching disadvantaged students is hard, said Kelly Gwaltney, principal of a high-poverty school in North Carolina’s Charlotte-Mecklenburg district. It’s even harder when students have missed months of instruction the year before.

Chicago Public Schools can’t find enough full-time teachers or substitutes, reports Sarah Karp on WBEZ. Schools with low-income and black students are “twice as likely as all other schools to have a yearlong teacher vacancy,” while “Chicago’s 28 schools with majority white student populations had no yearlong vacancies.”

Last school year, almost a third of 520 district-run schools — 152 — had at least one regular education or special education teacher position open all year long, a WBEZ analysis shows.

. . . Often, when there is a long-term vacancy, students get a parade of substitutes who might give them worksheets or worse — spend time sitting in an auditorium without any school work to do.

Substitutes, who are in short supply, have the turn to turn down assignments. “At 62 schools, half the time a teacher was absent no substitute showed up,” writes Karp.

Half of schools have an unfilled position for a special education teacher, WBEZ found. “Making matters worse for special education students, their teachers sometimes are pulled away from their students to cover for an absent classroom teacher.”

In a story on the Oakland teachers’ strike, the San Francisco Chronicle interviewed a substitute teacher. Greg Kalkanis said he’s taught Spanish full-time at McClymonds High for a year. He doesn’t speak Spanish.