The purpose of this study was to examine how 52 pre-service teachers (PSTs) assessed 7th-grade students' learning of social studies lessons they planned and taught. The PSTs provided assessment artifacts on 312 students, along with explanations for how they assessed and graded each student. Of the 429 coded assessment explanations, 240 (56%) related directly to students' social studies achievement, 141 (33%) related to non-achievement factors, and 48 (11%) related to achievement factors not connected with social studies. Consistent with previous research on the assessment practices of in-service teachers, the pre-service teachers in this study used a combination of student achievement, effort, behavior, and ability to make their grading judgments. Assessment of student learning is taking a greater role in education today, and much of the burden for helping new teachers to improve their assessment practices will fall on teacher educators, who should integrate explicit coursework on assessment with authentic field experiences for PSTs to practice planning and teaching lessons, as well as assessing and grading students.