For students: Learn about Copyright (elementary & middle school)
Specifically about images in school projects: Excellent article by Cult of Pedagogy
Copyright.gov's video learning series
Places to acquire images that are either in the public domain or licensed for noncommerical reuse:
For Holland Patent Students ONLY:
Copyright-friendly images for students and teachers:
Photos for class: free images, easily searchable, to use for educational purposes with credit easily attributed:
Most of the photos in this collection are public domain:
Pdphoto.org and pixabay.com (each image will let you know if you can use it and whether or not you have to cite it).
Wikimedia commons: This vast repository of images and sounds is just like wikipedia. Anyone can be a contributor, and it's FREE for everyone involved. Contributors believe in sharing their work instead of keeping their copyright protections at the forefront. Contributors have donated this material to the public domain--users may search for images and sound and use it based on the contributors stipulations, which often tell you that you can use their image/sound as long as you make your own work freely available as well. If you find an image or sound that you want to use, simply look at the rules for its use before you use, share, or modify it. Most likely, you will be able to whatever you want with it!
Free images to use under creative commons license (not for commercial use--can adapt, modify, use for educational purposes). Some photos are less professional than others; this is a good source for browsing beautiful pictures rather than trying to search for something specific:
NASA Library of Images - NASA should be credited as the source when you use the photos in this great library of high-quality images. Most of the images are in the public domain unless specifically noted--in those cases, you will need to obtain permission to use the photos from the creator of the image (it will be noted).
Clipart for Teachers - I love this site! It's great for classroom newsletters, your web page design, and you can even create your own teacher stationary! Perfect for elementary school teachers.
This one is not as great as the first--more basic and outdated, but if you can't find what you want from the one above, try this.