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At a California charter school where I once worked as a student teacher a few years ago, I saw a 16-year-old student curse at and threaten a teacher in the worst way. It wasn’t the first time I’d seen this type of thing, but this incident was particularly bad. The bell had just rung to change periods, and the halls were crowded. I have no idea what the argument was about, but the student flipped off the teacher and said “f— you!” As the teacher was trying to call a guard, the student walked back toward him menacingly and said: “You don’t have to call the guard. We can handle this right now.” This student wasn’t a first-time offender; he habitually bullied students and adults alike. It was baffling that, after all this bad behavior, the student was still allowed on the campus. Then I overheard a parent offer a disturbing explanation: “This is what $41 a day gets us.”

Forty-one dollars. That’s how much money that charter school receives per day for each student who walks through its doors. When a student doesn’t show up at school – whether it’s because of illness or a suspension – neither does that $41. That might not seem like a lot, but that money can quickly add up. Take a small charter school in a transient, low-income neighborhood: If it were to lose just 10 students over the course of the year – a few students transfer to other schools; a few families move out of the area; a few kids are expelled or become truants – the school would be docked about $75,000. That could be the equivalent of two teachers’ salaries. For a cash-strapped school serving a lot of at-risk students, that is a death blow.

Traditionally, public schools are funded based on their total student enrollment. But California, Texas and some other states tie dollars to attendance instead, incentivizing schools to get as many students in their classrooms as possible. That has led schools to implement programs that dole out rewards to students for high attendance, from bicycles and laptops to performances by pop stars and $20,000 vouchers for a new car. It might sound like a noble effort: Students with high attendance are more likely to graduate, and absenteeism has been tied to crime and other social problems. But there’s a downside to keeping kids in school at any cost – often that cost is the well-being of teachers and other students.

An assistant principal at the charter school where I taught told me that the head principal was loathe to suspend any student, no matter how disruptive, and expulsions were extremely rare. The tiny, poorly funded charter desperately needed the money that came with each student marked present every day, even potentially dangerous ones.

Moreover, attendance-based funding formulas are most harmful to schools that serve high-poverty areas, those teaching students who often need expensive extra supports and resources to learn. Inner-city schools with larger numbers of single-parent households and higher crime rates suffer from higher rates of truancy, dropouts and suspensions than those in wealthier suburban neighborhoods. The result can be “financially staggering,” according to a study of San Diego public schools. That district loses $29 for each day a student isn’t in class – a number that ballooned to $102 million in the 2009-2010 school year. The district was shortchanged $624 million over five years as a result of attendance-based funding.

Some may argue that this is good stewardship of public funds. Why pay money for a student who isn’t there? The cost of an enrolled student doesn’t disappear just because he or she doesn’t show up. Schools are staffed according to total enrollment, so even when a student isn’t present, the district is still responsible for the teachers’ salaries and the bills that keep the school operating. But that lost revenue must be cut somewhere, so after-school programs vanish, broken toilets go unfixed, and the school library is closed. Services that many low-income children don’t have access to elsewhere – music and art classes, breakfast, math tutoring – disappear.

As Congress debates this month the reauthorization of No Child Left Behind, the nation’s primary education law, lawmakers should consider how states distribute the federal funds they receive for schools. NCLB administers Title I funding, first established 50 years ago by President Lyndon B. Johnson in part to “meet the educational needs of low-achieving children in our Nation’s highest-poverty schools.” In the 2014 fiscal year, that amounted to $14 billion that should have been dedicated to providing extra educational resources to low-income students. But in far too many cases, that money is just filling in where state and local funds fall short on providing the basics. A 2001 report from the Department of Education found that 40 percent of schools in high-poverty areas are shortchanged by inequitable state and local funding formulas, leaving low-income students with fewer resources than wealthier students nearby.

Attendance-based school funding hurts our most vulnerable students by pressuring educators to keep unruly – sometimes violent – children in school. Add to that the recent push to ban suspensions altogether, and the schools in our toughest areas feel no different from the rough streets that schools, at least in part, are designed to provide poor students an escape from.

These funding formulas put educators in a no-win situation: If they suspend or expel disruptive children, they lose out on money to provide educational services to other students who need it. If they keep misbehaving children in school, that threatens the safety of the staff and cripples the learning process. Teachers can’t teach when they are forced to babysit recalcitrant students in their classrooms. Allowing states to, in essence, punish the vast majority of students — those who are well-behaved and show up to school every day willing to learn — for the indifference or truancy of the minority who are chronically absent seems fundamentally unfair.

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