The Washington Supreme Court plans to issue a ruling Thursday on a lawsuit challenging the two-thirds majority rule for tax increases by the Legislature.

A King County judge decided last spring that the voter-approved initiative is invalid because the state Constitution requires only a simple majority to pass tax proposals.

A coalition of lawmakers and education groups sued the state over this issue. They say the two-thirds majority rule makes it too difficult for the Legislature to respond to the Supreme Court's earlier decision on the inadequacy of Washington state's education spending.

The Supreme Court agreed to expedite its consideration of the two-thirds majority rule, which came about because of a series of citizen initiatives.

The Washington Constitution requires a simple majority of the Legislature to approve most laws.