Forces all Google Image searches to be for images free of copyright restrictionsCraftyRights forces image searches using Google Image Search to return only results labeled for reuse. While I make no guarantees, this extension may help mitigate concerns about students using copyrighted images.
To be more specific, the search returns images that are labeled for reuse. If you intend to modify the images or use them for commercial purposes, you may need to select a different license. Remember, the ultimate responsibility for licensing is yours.