WASHINGTON - The nation's largest teacher union joined school districts in Texas, Michigan and Vermont in filing a federal lawsuit Wednesday against the Department of Education for failing to provide adequate funding for the No Child Left Behind initiative.

The first-of-its-kind lawsuit is the latest in a series of legal challenges to the Bush administration's signature education reform, which aims to make every student in the country proficient in reading and math by 2014. On Tuesday, the Utah state legislature voted to give priority to its state school accountability system over the federal law in the event of a conflict.