The gap in academic achievement is not necessarily a result of bad teachers, but a result of inconsistent teachers.

According to a report from journalist Emma Brown of The Washington Post, low-income school districts are struggling to attract and retain quality, long-term teachers — forcing the schools to either use substitute teachers or to just not offer subjects at all.

City schools have such a high demand for teachers that vacancies often extend far past the beginning of the school year. Philadelphia is currently trying fill 136 empty teaching slots, while Detroit is attempting to fill 135, according to the Washington Post Report. Overall, urban schools end up filling one in six teaching slots after the school year begins — a rate of instability that can greatly undermine students’ education.

Seeing that they often have more vacancies to fill than more affluent schools, city schools usually fill teaching slots with younger, relatively inexperienced teachers. Consequently, many teachers end up starting their careers at low-income, urban school districts.

This pattern is the root of the problem — teachers who start at urban schools tend to use them as stepping stones to districts that may have been their first choice, but just weren’t hiring at the time. This causes a never-ending cycle of vacancies at inner city schools and leaves lower-income students, usually minorities, without teachers. The number of African-American and Hispanic students decreases, on average, by 14 and 20 percentage points from urban to suburban school districts, according to data from Education Next, a journal of opinion and research about education policy.

This trend helps to keep children at low-income city schools in cyclical poverty. It prevents them from receiving consistent, quality teaching in essential subjects they will need to succeed later in life. Inconsistent teaching keeps these schools at the bottom of standardized test scores — meaning they are at the bottom of the state’s budgetary priorities, further damaging the students’ quality of education.

As David Sapp, director of education advocacy and legal counsel at the American Civil Liberties Union of Southern California, told The Washington Post, “There are a narrow set of schools where this happens all the time, and until that gets really unpacked and resolved, there’s only so much that can be done to close the achievement gap.”

In other words, we cannot close the education achievement gap until we start getting teachers to stay and make careers at disadvantaged schools.

In order to ensure that every student has access to consistent teaching, we must better incentivize teachers to forge careers at urban schools. For instance, the government could offer student debt relief for teachers who decide to go to, and stay at least five years at urban schools after college. Another policy would be for the state to provide better funding for urban school teacher salaries.

Quality of education shouldn’t depend on location. Government funds need to help fill in the gaps of too-frequent vacancies.