Budget constraints and limited supplies of local tutors have caused many K-12 school districts to pivot from individual tutoring in-person toward small-group tutoring online to expand access to personalized instruction. We conduct a field experiment to explore the effect of increasing student-tutor ratios on middle school students' math achievement and growth during an online tutoring program. We leverage a novel feature of the program where tutors often taught individual and small-group tutoring sessions, allowing them to directly compare their experiences across these settings. Both experimental estimates and tutor survey responses suggest 1:1 tutoring is more effective than 3:1 tutoring online. Tutoring small groups in an online format presents additional challenges for personalizing instruction, developing relationships, fostering participation, and managing student behavior.