The widespread concerns teachers have expressed about some aspects of a proposed new grading policy in the Chapel Hill-Carrboro School District sends up a big red flag.

The proposed policy is intended to make grading practices consistent in high schools throughout the district. It includes several provisions, the most controversial of which would restructure the 0-to-100 numeric grade scale; under the new scale, the lowest possible score a student could get would be 61.

That may look at first glance like an arbitrary number, but there is a rationale behind it. The idea is that letter grades would fall along a consistent seven-point scale: 93 to 100 for an A, 85 to 92 for a B, 77 to 84 for a C, 69 to 76 for a D, and 61 to 68 for an F.

In other words, 61 is the new zero. Officials say the new system would help kids recover from one missed assignment or blown test.

The new grading proposal drew a lot of opposition from teachers at the district's high schools. School board officials heard more criticism Thursday night from parents and students.

The teachers' concerns carry the most weight. They're the ones in the most direct experience and involvement with students. They know how students learn, and they know how to evaluate what students have learned.

One of the problems with the proposed new scale is that it would award the same number of points -- 61 -- to a student who slept through an exam and turned it in blank as it would to a student who studied and tried hard but came just shy of reaching passing level. Does that seem fair? A number of teachers said the new system could have the effect of discouraging students from making their best effort rather than encouraging them to do so.

Among the other measures in the proposed policy would be a requirement that homework count no more than 20 percent of overall grades.

That might be appropriate for some subjects but not for others. In some subjects, such as English, outside-of-class reading, research and writing form a major part of the workload. Are teachers to be limited to counting all that work for only 20 percent of a student's grade? Even the definition of "homework" varies from subject to subject.

A requirement that all teachers in all subjects use the same measuring stick fails to recognize the inherent differences in how various subjects are most effectively taught and evaluated, not to mention the differences in how various students are best taught and evaluated.

That's one of the difficulties with the drive to "standardize" everything in education. Yes, you want consistency. Yes, you want to require students to reach certain standards of achievement.

But there's a point at which that effort can become overly rigid, limiting teachers' ability to do what they do best: use their judgment, experience and creativity to help young people learn.

We're blessed to have a remarkable number of gifted teachers here. The classroom is their turf, and they know what they're doing. When the district considers making significant changes in the way teaching and grading are done, it would be wise to draw on that expertise, and to listen closely to what they have to say.