Graduate students in science technology, engineering, and mathematics (STEM) fields often enter degree programs focused on research or field-based experiences. Being a teaching assistant can serve two purposes: one for financial compensation and two as preparation for teaching in a future career. The GK-12 program (Graduate Teaching Fellows in K-12 Education) funded by the National Science Foundation offers graduate students unique teaching opportunities as students are paired with a teacher in a K-12 classroom. Results from our sample of graduate students funded over a 10-year period document the benefits for teaching fellows in numerous areas such as communication with various audiences, collaboration with other teaching partners, and confidence in their ability to teach and engage students. Additional benefits were found, such as exposure to the K-12 educational system, changes to dissertation topics, and (unexpectedly) a modest group of students who found teaching in the K-12 system to inspire them to seek these positions. An equal number of students indicated that outreach to the K-12 system would be part of their professoriate or, for a few, their sole position as an outreach educator/coordinator. Quantitative and qualitative statements support the findings and offer insights into the unique aspects of working as a graduate student in K-12 education. (Contains 3 tables.)