Different universities, colleges, and high schools have different standards. What is good and allowed for one, will be a red flag for another one. Mostly, no more than 20% of text coincidence can be tolerated, while more means the text is not original. Although, even if that 20% is just a single copy-pasted piece of text, it’s considered borrowed.
DawsonITE is a blog devoted to Educational Technology. It's compiled by Rafael Scapin, Coordinator of Educational Technology at Dawson College in Montreal (Canada).