Standards-based grading (SBG) is a grading system in which each student is given a set of grades, each reflecting their proficiency in relation to a specific skill. The present study examined K-12 teachers' implementation of SBG practices in a small, suburban Midwestern school district, as well as their perceptions of and confidence in implementing SBG. It also examined these teachers' prior formal and informal opportunities to learn about SBG and how both pre-service and in-service opportunities to learn relate to their implementation of SBG. Results provide evidence of mixed levels of teacher SBG implementation, mixed teacher perceptions of SBG, and mixed teacher confidence in implementing such practices. In addition, the study finds that teachers' prior opportunities to learn about SBG practices formally and informally were variable. Participation in both pre-service and in-service opportunities to learn about SBG were moreover related to SBG implementation, and these relationships were partially or fully mediated by teachers' confidence in implementing SBG practices.