SIOUX FALLS, S.D. (AP) — A Michigan-based conservative Christian advocacy group has filed another lawsuit over states' membership in an organization supporting federally backed Common Core education standards.

The Thomas More Law Center sued South Dakota and several state officials in Hughes County over South Dakota's membership in the Smarter Balanced Assessment Consortium, which developed the standardized tests.

The suit filed on behalf of three South Dakota plaintiffs claims that the state's participation violates a part of the U.S. Constitution preventing states from entering into agreements or compacts with other states. Similar lawsuits were filed in North Dakota and West Virginia.

Common Core outlines skills students need to be ready for college and careers. South Dakota offered new Smarter Balanced standardized tests this year.

A governor's spokesman said the state doesn't comment on pending litigation.

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