Fewer than one-quarter of Missouri's 520 public school districts are using a new staff evaluation model developed by the state Department of Elementary and Secondary Education.

The department says half of the districts are using their own evaluation systems that align with the seven key evaluation principles developed by the agency. It says 28 percent are using an evaluation model developed by the University of Missouri and 22 percent are using the state's model.

One of the state's new guidelines calls for student performance measures to be used when evaluating staff.

A proposal on Missouri's November ballot would require student performance data to be the majority factor in staff evaluations that are used in determining which teachers to retain and how much to pay them.