I wondered this a long time ago.
Earlier this month, the Washington State Supreme Court issued a nine-page evaluation of the legislature's fulfillment of its obligation to meet its consititutional and paramount duty to amply fund public education–which as a reminder, is what the ruling in McCleary, et al. v State of Washington concluded back in 2012.
You have to wonder what the Supreme Court will, or even can, do if the legislature doesn't take appropriate action. Even though several of our legislators believe that the Court has overstepped its authority, as this article from the Seattle Times mentions, there are some other states where the highest court issued orders to their state legislature to take action to rectify some discordance. From the Times (linked above):
The reality is, no one knows exactly what the court would do.