Howlett v. Rose
In Howlett v. Rose, 496 U.S. 356 (1990), the U.S. Supreme Court held that a state court could not refuse to hear a Section 1983 suit against a school board on the basis of sovereign immunity. The school board was not an arm of the State, however, so it could not assert any constitutional defense of sovereign immunity to which the State would have been entitled. See Mt. Healthy City Bd. of Ed. v. Doyle, 429 U.S. 274, 280 (1977).
Justice John Paul Stevens wrote this unanimous opinion, which was remarkable in ordering a state court to accept jurisdiction and reject a state defense. The question was "whether a state-law defense of 'sovereign immunity' is available to a school board otherwise subject to suit in a Florida court even though such a defense would not be available if the action had been brought in a federal forum." 496 U.S. at 358-359.
The decision did not address the question of Congress' power to compel a state court to entertain an action against a nonconsenting State, which was addressed later in Alden v. Maine.