Moving to Germany - French school for my son

Hey InterNations ...

Planning to move to Germany soon , I am preparing well for my A2 language certificate , but worried about my "French educated" son.

How can i let him transfer smoothly to german when we move in?
Tried the best way , to find international school that teach French (main) & German (second language), so he can find his way easily... couldn't find any ...

Any Advise ?

NB: checked locally here in Qatar, there is one after school class , but don't wanna rely only on that option , my question is about any solution in Germany itself?