American private high schools are buzzing about something called the mastery transcript — a way to replace traditional letter grades with digital, evidence-based records of each student's academic achievements and character strengths. And it would be used in the college admissions process.

When schools such as Andover, Miss Porter's, Chapin and Holton-Arms where annual tuition is more than $40,000 — start talking about changing college admission procedures, commentators understandably wonder if they want to muscle out those of us who could only afford the neighborhood high school.

My Post colleague Catherine Rampell has concluded the mastery transcript "would have at least one pernicious effect: It would probably help mediocre (generally rich) prep school kids and hurt high-achieving (generally less well-off) public school students."

She is wrong about that. The most selective colleges reveal annually what percentage of their incoming students are from private high schools. Already under fire for not admitting enough low-income students, they would never let their percentage of rich kids increase.

The Mastery Transcript Consortium includes 160 private schools and plans to admit public schools soon. It is smart and brave of those educators to challenge the standard American A-to-F slapdash assessments and commit to subject mastery for each student. Some of the best teachers I know want to make sure every student learns the essentials no matter how long it takes. Just putting a grade on a report card at the end of the school year feels to them like giving up.

That mastery approach is absent from nearly all of our high schools, including those that cater to senators' and billionaires' children. Why can't we adopt the same attitude toward learning high school math, science, history and English that we do toward young students learning to read? Most elementary schools have specialists to get every child over that hurdle, while we shove students who struggle in high school courses off to the next grade with just a concerned look and a low mark.

Advocates of mastery learning want to encourage projects — such as designing a school building or reenacting the Constitutional Convention — that don't lend themselves to report card grades. They hope their new transcript will spotlight character traits ignored by the traditional grading system. A panel at each school would have final say on each student's transcript. Individual students and families could choose to use the new mastery transcript or stick with the old one.

The consortium says it has "organized around the development and dissemination of an alternative model of assessment, crediting and transcript generation" that will "demonstrate a mastery of skills, knowledge and habits of mind by presenting evidence that is then assessed against an institutionally specific standard of mastery."

Attempts to do that in the past have failed because they devoured so much time. But D. Scott Looney, head of Cleveland's Hawken School and founder and board chair of the consortium, said the old system provides almost no feedback "for the student to figure out how to improve," so some extra time would have great value in augmenting "the quality and depth of dialogue between the student and teacher."

Looney said college admissions officers could read the resulting online transcript in two minutes. If they wished, with a few more clicks they could see some of the student's actual work.

He said each school would decide how it wants to measure mastery. Independent measures of achievement, such as Advanced Placement and SAT exams, would remain. We could learn a great deal from the schools that try this.

But that won't make the college admissions system more rational or less stressful, because the most sought-after colleges will still be selective, and many applicants will still be disappointed. Looney acknowledged colleges won't accept the new transcript unless it helps them decide who the best applicants are from each high school.

Looney said some schools have so many straight-A students that the transcript could help separate the true geniuses from dogged grade-grubbers like me. Maybe, but when a student finds a classmate beat her out of a place at Yale University because of better "habits of mind," it's going to hurt just as badly.