JACKSON, Miss. — A Hinds County judge will let three groups that favor charter schools intervene in a lawsuit challenging whether such schools can legally receive Mississippi education money.

Mike Hurst, representing a group of parents from Midtown Public Charter School, says Chancery Judge Dewayne Thomas made the decision after a Wednesday hearing. Lawyers for the three groups who want to intervene — the Midtown parents, the Mississippi Charter Schools Association and Midtown Partners — are drafting orders for Thomas to sign.

Mississippi’s three charter schools, all in Jackson, are operated by private, nonprofit groups.

Opponents of the funding sued in July, represented by the Southern Poverty Law Center. They say charter schools are barred from getting state money because they are not overseen by the state superintendent or a local school superintendent, and thus under previous state Supreme Court decisions, don’t qualify as “free schools.” The state Constitution says only “free schools” can get public money.

The plaintiffs also say a 2007 Supreme Court decision bars the transfer of property tax collections from one school district to another. Each charter school is set up as separate district in Mississippi, meaning the three schools now operating aren’t part of the Jackson district.

Lawyers for the state say the act is constitutional.

Charter school supporters argue they have particular interests to defend. They will be co-defendants along with state government and the Jackson school district.

“Parents, children and their families have now been given a voice in this lawsuit that impacts them more than any other party in the lawsuit,” Hurst said in a telephone interview after the hearing.

The plaintiffs and Jackson schools argued for excluding them, saying more defendants would slow the case.

“Permitting intervention would lead to delay and increased costs, with no measurable additional benefit to the court’s ability to determine the single question of pure law presented here,” wrote Lydia Wright, an SPLC lawyer, in a brief filed Monday.

Thomas gave the parties three months to examine facts and set an April 4 hearing to see if he can decide the case without a trial. The SPLC says no trial is needed because the case involves only legal interpretation. But Thomas also set a trial date of May 22.

Hurst said he believes there might be disagreements over the facts, based on statements the plaintiffs made. He wouldn’t give details, saying he didn’t want to reveal his strategy in the lawsuit.

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