If you have an internet filter in place, you might have better luck preventing searches for translations by using your filter's keyword blocking options. Even if you do block Google's own translation services, there are plenty of other helpful sites out there eager to offer a translation right on the search page. For our school, we don't block these searches, but instead use them as an opportunity to start a conversation with the student as needed.
That being said, we do "block" Google's embedded translation service (as a side effect of blocking most of the other "smart" search features which there are no admin controls for). You do this by changing the setting "Omnibox Search Provider Name," under Devices > Settings. Set the dropdown arrow to the lock option, put Google (or whatever you'd like) in first two boxes, and then set the search URL to:
{google:baseURL}search?q={searchTerms}&udm=14&{google:RLZ}{google:originalQueryForSuggestion}{google:assistedQueryStats}{google:searchFieldtrialParameter}{google:searchClient}{google:sourceId}ie={inputEncoding}
Curtesy of: Random Tech Blogs