Richard Byrne recorded the following short video in which he shows three places (Pexels, Stockio, Pixabay) to find free video clips that you can download and share with your students to use in classroom projects.
See Richards's video and subscribe to his YouTube channel at youtu.be/-T8JKXPV7Qc
"Pexels Videos is a good place to find free video clips to use as background in green screen productions.
Pexels Videos offers hundreds of short videos that you can download for free and re-use in your own video productions. You can browse the collection or search according to keyword. You can also just jump to this selected collection of video clips suitable for green screen productions. The videos are stock footage and very few have any spoken words in them. To download a video from Pexels you just have to click the green download button next to the video you want to use. You don't have register on the site in order to download Pexels Videos. Attribution is not required for most videos, but double-check before using a video that you've downloaded from Pexels Videos." ~Richard Byrne Blog
Coverr offers free B-roll video clips that can be downloaded and used in projects. Most are silent and shorter than a minute. No registration required. Be sure students know to avoid those labeled Shutterstock.
"The Internet Archive is the first place that comes to mind when I am asked for a source of Public Domain media. The Moving Image Archive within the Internet Archive is an index of more than 1.7 million video clips. Most of what you will find in the Moving Image Archive can be downloaded in a variety of file formats. You can search the archive by keyword or browse through the many categories and thematic collections in the archive. One important thing to note about the Internet Archive is that you probably don't want students to search it without supervision." ~ Richard Byrne Blog