What exactly is an 'ineffective teacher?' California's definition doesn't include measures of performance

Even after years of debate and litigation over teacher evaluations and tenure, California had no official definition of what constituted a bad educator — until now.

Under the federal Every Student Succeeds Act, states must report on whether disadvantaged students have a higher proportion of ineffective, out-of-field or inexperienced teachers than do their peers. But to supply that answer, California needed to define, concretely, what an ineffective teacher looks like.

http://www.latimes.com/local/education/la-me-california-ineffective-teacher-20170712-htmlstory.html