Hi Michelle,

That's an interesting example because it depends on what you are trying to say -

Vous faites tous vos devoirs = You are all doing your homework 

The -s is pronounced as it means all of you and it reiterates the vous, subject of faire in that sentence.

But if you said to children for instance -

Faites tous vos devoirs! = Do all your homework!

The 'tous' apply to devoirs and agrees with the noun devoirs and is the object of faire.

In this case the -s is not pronounced.

Take a look at the following Kwiziq lesson with more in-depth explanation -

https://kwiziq.learnfrenchwithalexa.com/revision/grammar/tout-tous-and-toute-toutes-all-all-of-them-the-whole-indefinite-pronouns

Hope this helps!