This paper introduces StudyChat, a real-world college student dataset collected through interactions with a tutoring chatbot based on a large-scale language model (LLM). We collected 16,851 interactions with an LLM-based web application while students were completing programming assignments in a college-level AI course and annotated them using a conversational act labeling technique. Data analysis revealed that students who used the LLM for conceptual understanding and coding support performed better on assignments and exams, while those who used it for report writing or to avoid assignment learning objectives performed worse on exams. StudyChat can serve as a shared resource for further research on the role of LLM in education.