It’s hard to say whether it’s is morally correct to report against your friend to the school authorities. Because you don’t know the real scenario. May be he was busy and couldn’t manage to do his report of his own. Also, there is a possibilities that he has written that essay by his own and hired a essay writer for proofreading and grammar checking.
Now a days, many students hire essay writer. Top students also hire editors to achieve high marks. I think there is nothing wrong to get assistance from a editor to prepare a perfect assignment or report. I personally use writercheap.com/ services and pretty satisfied with marks and quality