The advantages of using free for education material include:
Note that you still need to comply with any applicable licence terms in relation to free for education material.
Regardless of the licence or statements that no attribution is required, you should always label any content used. Follow the guidelines:
Open Education Resources are teaching and learning resources available under legally recognised open licences. They are free for people to reuse, revise, remix, and redistribute (depending on the licence type). Many utilise Creative Commons licences.
Information from Smartcopying about OER resources
Creative Commons, Australia (2012), What are the Creative Commons licences? factsheet, accessed from: http://creativecommons.org.au/weblog/entry/244