A system that measures whether public schools are properly educating kids should be straightforward.It should be credible, accurate and easy to understand.If only.Texas' accountability system, designed to ensure that schools got better, that poor performance had consequences and that struggling students didn't get hidden, became so punitive, burdensome, misleading and test-obsessed that lawmakers demanded something different.With the State of Texas Assessments of Academic Readiness being phased in to evaluate how well students are learning, education officials still must devise a method of using those scores to evaluate how well schools are performing.It's complicated.A lot of public debate has centered on how much STAAR end-of-course exams count in high school students' grades, and the Legislature this session almost certainly will revisit its 15 percent requirement.But, more fundamentally, state education officials must figure out how to use STAAR results and other factors to get a reliable reading that pinpoints problems but also promotes improvement.The Texas Education Agency and committees of educators have spent the past year developing a new accountability rating system. The goal is for Education Commissioner Michael Williams to make final decisions by the end of March.TEA is accepting online public comments on the proposals through Friday here: bit.ly/XWUP5p.The materials developed so far (available online at bit.ly/wAOCRx) show a significant shift in emphasis that's intended to avoid what became weaknesses of the previous system that was based on the Texas Assessment of Knowledge and Skills.The TAKS-centered ratings focused primarily on scores of student groups -- African-American, Hispanic, white and economically disadvantaged -- on tests in English/reading, writing, math, social studies and science. If any group didn't meet the required standard on a test, the school's performance was rated unacceptable. A school also could be marked down for dropout or completion rates.The numbers also led to flawed short-hand: comparing the passing rates of one year's fifth-graders to the previous year's, for instance, provides limited information about whether a school is improving or regressing.Though students took STAAR tests in 2012, no ratings were issued, which gave schools a transition period.The new system will rely on a "performance index" that takes into account how well schools are doing on four basic criteria: results on the STAAR tests; closing racial achievement gaps; individual students' academic growth from year to year; and whether students are college and career ready when they leave.More groups will be evaluated, including English language learners, students with disabilities, American Indians and Asians, but no single factor will result in an unacceptable rating.Under STAAR, students in grades 3 through 8 still test in English/reading, writing, math, science and social studies, but high schoolers take 15 end-of-course exams.In a TribLive interview with Texas Tribune Editor-in-Chief Evan Smith on Thursday, Williams said he agreed that "the current system, based upon the weakest link, is an oppressive system." (bit.ly/UDE20T)That's been a widely heard criticism from superintendents and teachers who say it didn't give credit for progress made. One attempt to do that, the Texas Performance Measure, backfired because critics said it inflated scores."We can design a system that has a great deal more agreement as to its validity," Williams said.The evaluation mechanism should encourage teachers and administrators to focus on the curriculum, rather than on test-taking. It should help schools better prepare Texas high school students for the world they're going to face. And it should provide the public with a reliable understanding of how well those goals are being accomplished.