Iylarose Willis, a first-grader at Portland's Longfellow Elementary School, reads a book at a table in her classroom in this Jan. 25, 2017, file photo.

Let’s start from what I hope is a point of agreement: The role of public school is to equitably educate all students to a high level. To that end, schools across the state of Maine have chosen to pursue the state’s option to implement a proficiency-based graduation system (requiring students to demonstrate achievement of a common set of graduation standards) in lieu of a traditional system that assumes credits equate to learning, which many of us recognize from our childhoods.

But let’s not mistake what is familiar for what is equitable. After all, traditional credit-based systems have failed to accurately and fairly assess whether every student understands the material they need to succeed at college, in their career or as a citizen.

According to the Common College Completion Metrics, compiled by Complete College America, 24 of every 100 students starting college (at four-year institutions nationwide) are enrolled in math remediation; 12 are enrolled in English remediation. The statistics for those starting at two-year institutions are even worse. In other words, a large portion of high school graduates educated in traditional credit-based systems are not ready for college or the adult lives they are meant to embark upon.

History can help us understand why. Credit hours were designed in the late 1800s as a way to standardize the high school experience and increase the reliability of the college admissions process. Achievement of credits was based largely on the time students spent in class, not a common or explicit evaluation of their mastery of the material.

For a credit-based system to equitably educate all students to a high level — the expressed purpose of public education — we must assume similar amounts of time naturally result in similar levels of proficiency across all students with dissimilar learning capacities. Are we really comfortable making this assumption when the evidence indicates it’s not true?

Traditional grading methods also fail the students we are supposed to be educating. By averaging grades throughout a course, we reward students who start at a higher level of proficiency and punish those who may end up similarly skilled but who’s initial performance was lower. Is that fair? Or even logical? In addition, we routinely consider attendance, homework, extra credit and participation when assigning a course grade (rather than explicitly naming and grading relevant skills). While well-intentioned, this potentially allows students with huge learning gaps to erroneously pass courses.

These are just a few of the problems that proficiency-based education is designed to address. More still, proficiency-based education leads us closer to true educational equity. Whereas the old system is designed to educate some kids to a high level, proficiency is designed to educate all kids to a high level. How? By requiring every student to demonstrate their learning. Also, by defining success as the achievement of expected standards, not relative measures of performance or student-to-student comparisons.

Concerns about implementing proficiency-based education are not unfounded. Admittedly, occasional implementation missteps and misunderstandings have occurred. The solution is not to revert to an old system that wasn’t working; it is to renew our commitment to progress and innovation in the classroom. It is to clarify that proficiency-based systems don’t require switching to a 1-4 grading scale. (Yes, schools can choose to keep letter grades and commit to proficiency at the same time.) It is to remind families that proficiency-based diplomas don’t negatively impact a student’s chance of getting accepted to college. Most of all, it is to remind each other and ourselves what proficiency-based education is all about: Challenging students to learn deeply and to prepare for real life.

David Ruff is executive director of the Great Schools Partnership in Portland, and a founding member and director of the New England Secondary School Consortium, a six-state partnership working to promote forward-thinking innovations in secondary education.