Do We Need Formal Contract for Private School Permission?

Dear Rich: I work for a fully online private school and am seeking permission to use images, videos, and links within the course. Do I need to have a formal contract with a signature confirming that permission is granted to use the item, or is it enough to have an email response saying that they grant permission for our suggested use? 
The copyright law says that you need a writing signed by the copyright owner or his or her agent to transfer or license any of a copyright owner's rights. The signature can be handwritten or it can be a digital or electronic signature. If the email contains permission and is "signed" by the person who has authority to grant rights, your collection of emails is probably fine for permission purposes.