BOISE, Idaho (AP) — Ten Idaho residents led by the chairman of a conservative free-market think tank are suing the state over Common Core education standards.

In the lawsuit, Idaho Freedom Foundation board chairman Brent Regan contends that Idaho's participation in an agency that helps test and implement Common Core standards is illegal under federal rules governing agreements between states.

The Smarter Balanced Assessment Consortium includes about 19 states and territories as members, and in exchange for membership dues the states get access to curriculum tools and assessments. Similar lawsuits have targeted the same consortium in Missouri and North Dakota.

A state judge in Missouri ruled in February that the state's membership in SBAC was illegal and that payments must stop; that ruling is under appeal. The lawsuit in North Dakota is ongoing.