“To hear Trina’s counselor say they haven’t offered a senior science class for the LAST THREE YEARS, I am flabbergasted. Then they wonder why their students have to take remedial classes their first year of college, while students from nearby towns can get right to work on classes that count toward their degrees.”

Recently, I saw these words on a friend’s Facebook wall about her daughter’s school. Turns out, one of the reasons the school didn’t offer a senior science class is that there was no teacher to teach it. This school had churned through a series of four physics teachers in less than a decade. When the last physics teacher left, the school still didn’t have a replacement several weeks into the year, so they hired a teacher who had to be emergency certified to teach science. Since then, the school just stopped offering a senior science course. Trina’s situation is a stark example of the impact that high teacher turnover has on students’ opportunities to learn.

So why have so many teachers left? On average, teachers are more likely to leave a school when they’re dissatisfied with the school leadership and staff cohesion. In high-poverty schools like Trina’s, average teacher turnover is especially high — almost twice as high as in low-poverty schools, and the difference in turnover is worse for science and math teachers than in the humanities. But that pattern isn’t inevitable: when teachers are satisfied with their working conditions, they’re nearly as likely to stay at a high-poverty school as in a low-poverty school. In rural schools like Trina’s, where many teachers have limited access to medical services, family networks, and shopping, they also tend to leave at higher rates. Regardless of the reasons, teacher turnover means students don’t have the opportunity to take the rigorous courses necessary for many postsecondary pathways. For Trina, the shortage of science teachers is an extra hurdle to meeting her goal of helping address a dire need in her Native, rural community for culturally sensitive medical professionals.

In the coming weeks, states will identify struggling schools that need to improve, and those schools will start writing their improvement plans. Challenges like lack of support for teachers, chronic teacher turnover, and teacher shortages are often why struggling schools can’t offer rigorous courses. Advocates have an important role to play in pushing for equitable access to strong teachers to be central to school improvement efforts by asking questions about how school and district leaders will support teachers and in pushing schools, districts, and states to prioritize the needs of students being most underserved. That’s true in schools like Trina’s — a rural school serving primarily students of color from low-income families — and in schools with a more diverse student body but where students from historically underserved groups are being underserved. Ed Trust’s guide on Recruiting, Equitably Assigning, and Retaining Strong Teachers for School Improvement recommends questions for advocates to ask district and school leaders and what to look for in the answers.

Fortunately, Trina’s family has the academic experience to know that not having a science course her senior year would put her at a disadvantage in pursuing a science major in college and the STEM career through which she hopes to give back to her community. They are willing to push the guidance counselor to create a dual enrollment option through a nearby community college. In the three years since the school hasn’t offered a senior science course, Trina is the first student to ask for the dual enrollment option. This means that dozens more students have fallen through the cracks — a situation that would be unimaginable in many schools with more affluent, White students or ones that are less geographically isolated. But no young person should start the school year having to fight just to get what other students are able to take for granted.