Oh good point! And if you don't know the context when performing the translation (perhaps it's an announcement at an all-girls or an all-boys school?), then the translation will be incorrect.

The ambiguity in the original sentence may be impossible to preserve in the translation process, which doesn't mean that translation is impossible, but it does mean that information must be added by the translator to the sentence that wasn't present in the original sentence.

Sometimes I do small contract translation jobs as a side activity, but it's very frustrating when a client sends me snippets of text to be translated without the full context.