In recent years, reformers have sought to improve our failing public education system by tightening and standardizing the measures we use to judge performance. From the numerical requirements of the No Child Left Behind Act to California"s increased focus on assessment and accountability, there"s been a conscious attempt to use hard data to measure success at every level of the education system. But one group does not have its performance measured this way: teachers. Determining the effectiveness of individual teachers—are they helping our kids learn or not remains a mostly subjective judgment. Yet there"s no reason why teachers shouldn"t also be evaluated against objective measures of student performance just as are schools, districts and states. Teacher evaluations focus on what they do in the classroom—the input of the learning process. In most school districts, principals show up at prearranged times to observe teachers" work, and then write their observations. In doing this, they typically use a checklist to guide their assessments. Evaluations usually consist of one or two written observations. This superficial and largely subjective approach to evaluating teachers is something of a farce. In many instances, principals can only rate teachers "satisfactory" or "unsatisfactory". Multiple unsatisfactory evaluations can lead to dismissal. But faced with the prospect of battling the local teachers union to prove that a teacher"s unsatisfactory evaluation is valid, most principals capitulate and rate virtually all teachers as satisfactory. This rubber-stamp routine may make things easier for administrators, but not for the kids. Several researchers, among them Eric Hanushek of the Hoover Institution of Stanford University and Jonah Rockoff of Columbia University, have shown that teachers are not interchangeable when it comes to student learning. Given a year with an effective teacher—one whose pupils previously showed test-score gains—students can advance their learning by a grade level or more, according to research done by William Sanders while he was at the University of Tennessee. He also found that under a weak teacher, kids" progress can stall, and they can fall behind. So why not include student test scores—the output of the learning process -in teachers " evaluations Besides giving the evaluation process a much-needed shot of objectivity and rigor, this change could help administrators target assistance for struggling teachers and recognize those who are most effective in the classroom. In its report this month, Gov. Arnold Schwarzenegger"s nonpartisan committee of education experts agreed. Among other things, it recommended that teacher evaluations should be based in part on student achievement. The author proposes that teacher evaluations should______.

A. provide much assistance for struggling teachers
B. be based on the output of the learning process
C. be as much impersonal and unbiased as possible
D. recognize the most effective teachers in teaching