On June 25, 2018, the Kansas Supreme Court held that the legislature's efforts to increase school funding still failed to provide an adequate education for students in Gannon v. State of Kansas, et al., No. 113,267 (2018). According to the Supreme Court, the adequacy requirement in Article 6 of the Kansas Constitution is met when "the public education financing system for grades K-12 – through structure and implementation – is reasonably calculated to have all Kansas public education students meet or exceed the standards set out in Rose and presently codified in" Kansas statutes. The Supreme Court found the state's changes fell short of the adequacy mark because they: (1) failed to adjust two years of funding for inflation; (2) failed to adjust for inflation until the calculated principal sum issued by the Kansas Legislative Research Department was paid in full; and (3) reduced virtual school state aid by $31.2 million.

The Supreme Court acknowledged that proposed changes to the funding formula increased the dollars driven to "at-risk" students, funded all-day kindergarten, appropriated money for an ACT program, and increased the base aid amount. Nevertheless, the Supreme Court ruled these changes were not "persuasive on the issue of adequacy." Accordingly, the Supreme Court retained jurisdiction and gave the state until June 30, 2019 to address the issues raised by the Supreme Court.

A previous cost study commissioned by the Gannon plaintiffs concluded $1.58 billion dollars of additional funding was needed to achieve constitutional compliance. The legislature initially attempted to fund this increase by scheduling an additional $854 million dollar state appropriation and granting school boards increased authority to raise funds through additional property taxes or local option budgets. However, the Supreme Court rejected this approach, holding that reliance on increased local authority was "uncertain" because "each of the 286 districts has the discretion to determine how much of its authority it will use."

Following the rejection of its first approach in Gannon, the Kansas legislature commissioned its own cost study to determine the amount of additional funding allegedly needed to reach constitutional adequacy. The legislature's study employed a cost function approach, a method that generates estimates on what it would purportedly cost to achieve specific performance outcomes like graduation rates or testing proficiency. Ultimately, this cost function study concluded that an increase of $1.786 billion - $2.067 billion dollars was required. The funding framework rejected in the Kansas Supreme Court's most recent opinion was based in large part on the recommendations and findings of the legislative cost study.

The Supreme Court's latest ruling only contributes to escalating tensions between the legislature and judiciary regarding school funding. The conflict began following the Montoy v. State decision, in which the Supreme Court threatened to enjoin funding and close schools if the legislature did not increase school funding. The legislature responded by passing constitutional amendments denying court authority to enjoin such funding. Following the original Gannon decision, the legislature has worked to enact legislation satisfying court mandates, but this most recent holding has lawmakers revisiting the idea of using constitutional amendments to block judicial review of school funding legislation. Legislators contend the judiciary is overreaching because the legislature is in the best position to decide how schools are funded. Groups such as the Kansas Chamber of Commerce have formed the Coalition for Fair Funding to lobby for an amendment granting the legislature sole authority to determine school funding. While it is uncertain whether such an amendment is politically or legally feasible, it is representative of conversations occurring across the nation regarding judicial authority over what level of funding is required to fund an adequate education.