Educational leadership demands that school leaders be able to communicate clearly and effectively in writing, both academically and professionally. Leaders of a Master’s in Educational Leadership (M.Ed.) program at a university in the southeast of the United States established an interdisciplinary collaboration with the university’s Faculty Writing Partners program to develop valid and reliable rubrics to assess graduate students’ writing abilities through critical task essays. The critical task essays connect required internship experience in each course with a targeted Florida Principal Leadership Standard (FPLS), coursework, and scholarly research. However, an objective performance measure for the critical task essays was lacking. Accordingly, a criterion-referenced rubric was developed to: 1) specify criteria for writing in relation to grammar, mechanics, and organization, 2) identify quality peer-reviewed research as evidence to support clinical experience, 3) effectively articulate in writing personal strengths, weaknesses, and plans for improvement towards mastery of the FPLS, and 4) provide consistency in expectations and feedback among professors and adjunct instructors. The rubric demonstrated validity and reliability, and likely led to consistently higher scores on both the critical task essays and, most importantly, the Florida Educational Leadership Examination (FELE).