Graduate assistants perform teaching, laboratory work, or research of a character that affords useful academic experience while permitting a full academic schedule of courses.
A full teaching assistantship usually requires 20 hours per week to be devoted to teaching and to the related activities of class preparation, grading, and consulting with students. See the section on Teaching Assistants for more information.
Research assistantships typically involve 20 hours per week during the academic year, but can be more during the summer. Caltech graduate students often receive a combination of teaching and research assistantships.