JACKSON, Miss. (AP) — The Mississippi Supreme Court has ruled that the Legislature does not have an obligation to fully fund a school budget formula that was put into law two decades ago.

The court ruled Thursday against 21 school districts that sued the state in 2015. They sought money to make up for years of shortfalls when lawmakers didn't fully fund the Mississippi Adequate Education Program.

The attorney representing the districts is former Gov. Ronnie Musgrove, who pushed the funding formula into law in 1997.

The formula is designed to give school districts enough money to meet midlevel academic standards, but it has been short-funded most years.

A Hinds County chancery judge ruled against the school districts in July 2015, saying that the formula is not a mandate. Justices upheld that ruling Thursday.