The most inexperienced and least qualified teachers continue to teach in schools with the highest-needs students in California ­— even though those students require the most expert teachers, and research has shown that the effectiveness of classroom teachers is the biggest in-school factor contributing to students’ achievement. The state lacks comprehensive data, but the most recent report from the California Department of Education found that districts with the most low-income students had 25 percent more inexperienced and underqualified teachers and teachers with a temporary intern credential than districts with the lowest numbers of low-income children. The disparity has widened amid the ongoing teacher shortage, when districts have hired thousands of teachers with substandard credentials. It has persisted because there has been little state pressure on districts to take action in the new era of local control, and no leverage by Washington, under the Every Student Succeeds Act, to force states to hold districts accountable for inequitable staffing patterns. “In the decade since the recession, we haven’t made a serious effort to invest in schools with novice teachers, when the research has been clear that their inexperience creates an opportunity gap for kids,” said Bill Lucia, CEO of the Sacramento-based, nonprofit, advocacy organization EdVoice. “California is not alone; most of the country has dragged their feet on what may be the most significant issue of resource inequity,” said John Affeldt, managing partner of the nonprofit law firm Public Advocates, which has sued the federal and state governments a half-dozen times over the past two decades over issues of underqualified teachers in low-income schools and those in which many students are performing poorly. However, that could change significantly in 2020. Sometime next spring, the state will have collected and will make publicly available comprehensive data detailing the numbers and percentages in every school and district of “ineffective,” “inexperienced” and “out-of-field” teachers—categories of underqualified teachers that federal law requires districts to count.