There is Past tence for "grow" in the English sentence, but there is no Past tence for this verb in the Russian one.
Seems, like it should be "Because it's time to grow up for you". I don't speak French, so I can't check the original.

@NNC

"It's time + past tense" means the same thing as "It's time for you to + infinitive" in English.

So I see you know English better than me :)

And you obviously know Russian better than me, I'll change the Russian version.

Bienvenue sur Tatoeba ! ☺

It's only the clarification , cause in Russian we can say "тебе", "вам", "ему" etc. Though we can say it also without a pronoun, if we apply to a definite person. But you use a pronoun "tu", so it seems logical to use it also in the Russian sentence.

This is not a complete sentence. You might consider changing it to something like:

Because it's time you grew up, you should try to get a summer job.

I only translated what was there, it is not a translation if you add meaning to it.