I think this is due to a recent change on the observation page. It no longer shows casual observations automatically.
See: https://www.inaturalist.org/observations?user_id=wachnin&place_id=any&verifiable=any
vs https://www.inaturalist.org/observations?user_id=wachnin
Hopefully they switch it back to where the &verifiable=any is the default when clicking on a users observation… Otherwise, you should be able to add &verifiable=any at the end of the url to get the full number, but that might be onerous to do with every single student