Yes you can! In October 2018, the U.S. Copyright Office established a final ruling that states educational institutions may caption media for accessibility purposes without fear of copyright infringement. This exemption only applies to educational institutions (K-12, college, or university) captioning media as an accommodation for students with disabilities under applicable laws. While you can caption media, your institution must adhere to the following protocols:
Reasonable efforts must be taken first to ensure that an accessible version of the video is not already available at a fair price and in a timely manner
Accessible media must be distributed to students in a way that prevents unauthorized further dissemination of the work
For more information about this ruling, please review Section 1201 Rulemaking (p. 89).