Chicago’s debt-ridden schools are running out of options.

The nation’s third-largest school district — whose credit rating has tumbled well into junk — must make a $721 million pension payment by June 30 and officials are scrambling to find the funds. Ending the year early, canceling summer school, and slashing classroom spending are all possible, the Chicago Board of Education said in connection with a lawsuit that’s seeking to wrest more cash from Illinois.

“They’re trying any way they can to try to make the state provide more funding,” said Daniel Solender, head of municipals at Lord Abbett & Co., which manages about $19 billion of debt.

A local judge Friday dealt a blow to the schools’ lawsuit against Governor Bruce Rauner and the state board of education, which challenges funding practices that have made the district the only one in Illinois that pays most of its pension costs. Cook County