This is taken from the NSF GK-12 Website:
The Graduate STEM Fellows in K-12 Education (GK-12) Program, managed by NSF.s Division of Graduate Education (DGE), provides funding to graduate students in science, technology, engineering and mathematics (STEM) disciplines to acquire additional skills that will broadly prepare them for professional and scientific careers in the 21st century.
NSF developed the GK-12 program recognizing that, in addition to being competent researchers, STEM graduate students must be able to communicate science and research to a variety of audiences. As the graduate students bring their cutting-edge research and practice into the K-12 classroom, they gain these skills which enable them to explain science to people of all ages, ranging from students to teachers. The graduate students also inspire transformation in the K-12 formal and informal learning environments and stimulate interest in science and engineering among students and teachers. NSF understands that STEM graduate students can contribute to the national effort to advance scientific knowledge through partnerships with K-12 communities.
Through the GK-12 program, institutions of higher education have had an opportunity to make a significant change in STEM graduate and K-12 education programs by creating strong and enduring partnerships.