My immediate thought to your comment was that "frosh" is actually very common and accepted slang for "freshmen". That said, I did not expect to see it in the article's lede – or in the president's official statement [0]:

> We will continue planning with the hope and expectation of bringing undergraduates back to Stanford at the earliest possible time. If public health conditions allow, we plan to invite frosh, sophomores and new transfer students to be in residence on campus for the winter quarter, and juniors and seniors for the spring quarter.

[0] https://healthalerts.stanford.edu/covid-19/2020/08/13/autumn...