A Manhattan judge has handed the United Federation of Teachers a temporary victory in its fight to add a question to the November ballot that, if approved, would set in motion a process to specify in the city charter the size of classes in schools. Putting aside for the moment the underlying fallacy that smaller classes lead to greater student achievement, this is not the type of diktat that belongs in the city’s basic document. As luck would have it, Mayor Bloomberg has the power to kick this question off the ballot because he has his own ballot question on the topic of non-partisan elections.

In years that a mayor proposes charter revisions of his own, the state’s Municipal Home Rule Law mandates that the mayor’s proposals “bump” others — so that too many questions do not distract voters. In 1998, Mayor Giuliani used this provision to thwart an attempt by the City Council to field a referendum that would have prevented him from funding the construction of a stadium for the Yankees at Manhattan. The Appellate Division of the Supreme Court of New York State upheld Mr. Giuliani’s interpretation. And there is no reason to think the court won’t again on appeal.

On the underlying question, New Yorkers have every reason to oppose the UFT’s proposal should it find its way before them on the ballot. The UFT’s referendum would establish a commission to propose City Charter language that would possibly limit class sizes to 18 students a class in grades K–3, 22 in grades 4–8, and 25 in high school. Such restrictions would tie the hands of every administration despite the fact that there is no scientific evidence to suggest small class sizes actually boost achievement. In fact, one of the most thorough studies on the subject was done by noted educational economist Caroline Hoxby, an associate professor of economics at Harvard. Ms. Hoxby conducted a “natural experiment” involving 1,035 schools in 165 districts over 20 years in Connecticut. Using the natural fluctuation in the number of students entering a class each year, she created a sample with little statistical noise. A family might have one daughter in a first-grade class of 25 students, and her younger brother, two years later, might have only 18 students in his first-grade class. The students in this study were coming from the same economic background and sometimes had the same teachers. The result: no difference between students in small and large classes.

This mirrors the national trend. America has been reducing class sizes steadily for the last half-century, as education economist Eric Hanushek, of the Hoover Institute at Stanford University, notes. Despite a 35% reduction in student-teacher ratios, scores on the National Assessment of Educational Progress have remained stagnant from 1970 to today. New York has no reason to throw good money after bad padding the ranks of the United Federation of Teachers.