That's not my student in the photo.

Oops, Waldo's glasses must have gotten fogged up! But no worries, you can untag any photos directly from your app. 
Here are the instructions on removing an incorrect tag:
1. Open the Waldo Photos app and select the incorrect photo. Once it brings up the full sized photo, tap the photo to reveal several icons.
2. At the top of the screen you will see a “tag” icon which you can tap on.
3. A popup will then appear and you will see the name appear and you can tap and remove the tag.