How well students perform academically would count for as little as one-quarter of a teacher's evaluation next school year, if Chicago Public Schools becomes the first district in Illinois to implement new teacher assessments.

That's one proposal advanced by the state Board of Education on Friday, part of a complex series of proposed guidelines for evaluating teachers and principals that will be open for public comment through the end of the year. After two years, the student growth component of the evaluations would jump to a minimum of 30 percent, still a far cry