SEATTLE (AP) – The Washington Supreme Court plans to issue a ruling Thursday on a lawsuit challenging the two-thirds majority required for the Legislature to pass a tax increase.

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 the issue, saying that the two-thirds majority vote required in the Legislature to raise taxes or close tax exemptions is unconstitutional. They say the 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.

Most people agree the state needs about $4 billion to fulfill its constitutional promise to fully pay for basic education by 2018.

The Supreme Court agreed to expedite its consideration of the two-thirds majority rule, which came about because of a series of citizen initiatives. Voters most recently approved the supermajority rule last November.

The Washington Constitution requires a simple majority of the Legislature to approve most laws, but the supermajority, or two-thirds vote, has been the law for tax increases thanks mostly to measures successfully pushed by initiative activist Tim Eyman.

The state constitution cannot be changed through the initiative process; a vote of the Legislature is required.