In what follows, we draw on research to describe three significant concerns with this plan.
Concern #1: CPS is not ready to implement a teacher-evaluation system that is based on significant use of “student growth.” For Type I or Type II assessments, CPS must identify the assessments to be used, decide how to measure student growth on those assessments, and translate student growth into teacher-evaluation ratings. They must determine how certain student characteristics such as placement in special education, limited English-language proficiency, and residence in low-income households will be taken into consideration. They have to make sure that the necessary technology is available and usable, guarantee that they can correctly match teachers to their actual students, and determine that the tests are aligned to the new Common Core State Standards (CCSS).
In addition, teachers, principals, and other school administrators have to be trained on the use of student assessments for teacher evaluation. This training is on top of training already planned about CCSS and the Charlotte Danielson Framework for Teaching, used for the “teacher practice” part of evaluation.
For most teachers, a Type I or II assessment does not exist for their subject or grade level, so most teachers will need a Type III assessment. While work is being done nationally to develop what are commonly called assessments for “non-tested” subjects, this work is in its infancy. CPS must identify at least one Type III assessment for every grade and every subject, determine how student growth will be measured on these assessments, and translate the student growth from these different assessments into teacher-evaluation ratings in an equitable manner.
If CPS insists on implementing a teacher-evaluation system that incorporates student growth in September 2012, we can expect to see a widely flawed system that overwhelms principals and teachers and causes students to suffer.
Concern #2: Educational research and researchers strongly caution against teacher-evaluation approaches that use Value-Added Models (VAMs).
Chicago already uses a VAM statistical model to determine which schools are put on probation, closed, or turned around. For the new teacher-evaluation system, student growth on Type I or Type II assessments will be measured with VAMs or similar models. Yet, ten prominent researchers of assessment, teaching, and learning recently wrote an open letter that included some of the following concerns about using student test scores to evaluate educators:
a. Value-added models (VAMs) of teacher effectiveness do not produce stable ratings of teachers. For example, different statistical models (all based on reasonable assumptions) can yield different effectiveness scores.  Researchers have found that how a teacher is rated changes from class to class, from year to year, and even from test to test. 
b. There is no evidence that evaluation systems that incorporate student test scores produce gains in student achievement. In order to determine if there is a relationship, researchers recommend small-scale pilot testing of such systems. Student test scores have not been found to be a strong predictor of the quality of teaching as measured by other instruments or approaches. 
c. Assessments designed to evaluate student learning are not necessarily valid for measuring teacher effectiveness or student learning growth.  Using them to measure the latter is akin to using a meter stick to weigh a person: you might be able to develop a formula that links height and weight, but there will be plenty of error in your calculations.
Concern #3: Students will be adversely affected by the implementation of this new teacher-evaluation system.
When a teacher’s livelihood is directly impacted by his or her students’ scores on an end-of-year examination, test scores take front and center. The nurturing relationship between teacher and student changes for the worse, including in the following ways:
a. With a focus on end-of-year testing, there inevitably will be a narrowing of the curriculum as teachers focus more on test preparation and skill-and-drill teaching.  Enrichment activities in the arts, music, civics, and other non-tested areas will diminish.
b. Teachers will subtly but surely be incentivized to avoid students with health issues, students with disabilities, students who are English Language Learners, or students suffering from emotional issues. Research has shown that no model yet developed can adequately account for all of these ongoing factors. 
c. The dynamic between students and teacher will change. Instead of “teacher and student versus the exam,” it will be “teacher versus students’ performance on the exam.”
d. Collaboration among teachers will be replaced by competition. With a “value-added” system, a 5th grade teacher has little incentive to make sure that his or her incoming students score well on the 4th grade exams, because incoming students with high scores would make his or her job more challenging.
e. When competition replaces collaboration, every student loses.