District officials say the mystery has been solved concerning why all teachers, nonclassroom instructors and administrators in Charlotte County were assessed as “effective” last week by the state in a five-tiered grading system.

According to Charlotte County school superintendent Doug Whittaker, the across-the-board scores were a result of the district using an old evaluation tool to conduct teacher evaluations last year. Under the previous tool, which has been in place for several years, teachers could only earn a “satisfactory” or “unsatisfactory” designation.