the trial court observed, so to enshrine the Learning Standards would be to cede to a state agency the power to define a constitutional right. Although some amici nevertheless urge us to adopt the Learning Standards as the definition of a sound basic education, plaintiffs make no such request. Rather, they contend that children are entitled to a meaningful high school education, one that provides the essentials we listed. Defendants maintain that plaintiffs are trying to set the requirements for a high school diploma as the constitutional floor, and thereby to make mastery of the Learning Standards -- which are being phased in as the basis for a high school diploma ( see 8 NYCRR 100.5) -- the test of a sound basic education after all. We do not construe plaintiffs' arguments as a request for a rule tied to whatever diploma requirement the Regents promulgate, however high; nor do plaintiffs need such a rule to prevail. The issue to be resolved by the evidence is whether the State affords New York City schoolchildren the opportunity for a meaningful high school education, one which prepares them to function productively as civic participants. This is essentially the question the trial court addressed, and we conclude that the Appellate Division erred to the extent that it founded a judgment for defendants upon a much lower, grade-specific level of skills children are guaranteed the chance to achieve. III. The Evaluation To determine whether New York City schools in fact deliver the opportunity for a sound basic education, the trial court took evidence on the "inputs" children receive -- teaching, facilities and instrumentalities of learning -- and their resulting "outputs," such as test results and graduation and dropout rates. This organization of the facts follows naturally from our summary of the "essentials" in CFE and was not disputed by the Appellate Division.[3] A. Inputs Teaching. The first and surely most important input is teaching. The trial court considered six measures of teacher quality -including certification rates, test results, experience levels and the ratings teachers receive from their principals -- and concluded that the quality of New York City schoolteachers is inadequate, despite the commendable, even heroic, efforts of many teachers. The Appellate Division reached a contrary conclusion based on its perception that principals' reviews of the teachers they supervise