by Richard Oelmann.
Installing a plugin - and clicking on the Update Database button as part of that process - shouldn't have any effect at all on the tables related to assignment submissions
Hmm - then if the students are all still enrolled, I would definitely go with Emma's suggestion to check the logs. Direct interference with the database is an outside possibility (unless you as site admin are the only one with direct access to the database, in which case you would already know if you'd done that ), but I would go to the logs first as Emma said.