Traditional classroom assessment practice often leaves students out of the conversation, exacerbating the unequal power distribution in the classroom. Viewing classrooms as autonomy-inhibiting is known to influence students' psychosocial wellbeing as well as their academic achievement. This is especially relevant in STEM fields where marginalized populations experience disproportionate rates of attrition and success. The current paper describes the use of a simple, piloted classroom intervention with the intention of incorporating student voice in the co-creation of assessment criteria, relative to participation evaluation. Undergraduate students in a STEM research methods design course took part in the intervention. Pre- and post-tests were administered to understand what effects, if any, the intervention had on student perceptions of power and attitudes towards assessment. Perceptions of power significantly increased from pre- to post-test, and qualitative feedback from the intervention were overwhelmingly positive. Limitations and suggestions for future research are also discussed.