This research project was designed to determine if the Model Cornerstone Assessment for Performance, Proficient level, published by the National Association for Music Education would be an appropriate tool to use to demonstrate student growth as one element of teacher evaluations, specifically the T-TESS. This study focused on four main research questions: 1. Does the MCA satisfy the Texas Essential Knowledge and Skills (TEKS) in music, and if so, which ones? 2. Does this assessment demonstrate student growth, and in what ways? 3. How do Texas ensemble teachers modify and use this assessment? 4. Does this assessment improve learning, and does it have transferable skills? The researcher conducted an embedded mixed methods design during spring 2017 in one Texas school district, using surveys and interviews to gather data concerning Questions 1, 2, and 3. Data for questions 2 and 4 was gathered through the evaluation of recordings from six participating bands, three treatment bands and three comparison bands. The treatment bands recorded two pieces of music each; one piece received direct treatment, and a second piece to test for possible transferable effects. Qualitative results show the band directors perceive this tool does satisfy the TEKS, and does demonstrate student growth. Each of the band directors successfully modified the assessment in some way. Quantitative data showed a significant difference in the pieces of music receiving direct treatment, although with only a small effect size (11.0%). [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]