San Mateo, Calif. -- Edmodo, the San Mateo-based developer of a free K-12 social learning network, said on Thursday it has raised $25 million in its third round of funding, led by new investor New Enterprise Associates (NEA). Previous backers Greylock Partners, Benchmark Capital, Union Square Ventures and Learn Capital also participated in the round, which increased its total funding to $47.5 million. Tony Florence, a general partner at NEA, has been named to the company's board of directors. Edmodo's platform allows teachers and students to connect with each other to share content and access homework, grades and school notices. The service currently has more than 8 million users.