If you have a network monitoring tool in place, you can verify what traffic is being generated in relation to what you are looking for. For the translation function you mention, investigate what specific service MS Office Word uses (or if it works) to make sure it is being used.
In the case of Google translator search for the
https://translate.google.com/ URL in the traffic of your network so you can confirm if the students are using it. You can do the same with any other browser-based translator. Finally, if what you need / want is to block this service, you can use web filtering (which uses categories) so you do not have to worry about consulting these services, as they will be blocked.