If you are teaching students to use a spaced-repetition (SRS) flashcard system, such as Anki, that operates across different platforms (i.e., PC to website to app), it is extremely important to train the students to sync (or connect) before and after every study session and every card making session on any device - basically any time they do anything with their SRS system. If the students do not sync correctly, then the data that exist in the different places will not be the same, and there will be conflicts later, which could cause them to either lose the new cards they made or any study progress.
The other SRS system that I am recommending for iDevice users, Flashcard Elite, does not have this problem with syncing. Although, there is related problem with adding new cards to a deck that I will write about later.
Always syncing before and after every use of SRS ensures that the data are always the same in every place and removes the risk of conflicts.
I learned this the hard way today when I forgot to remind my students to sync at the beginning of our computer lab today - kind of embarrassing...