Moving to France for two years - Q on schools

My husband is looking at Industrial PhD options in France (We are still awaiting admits).
We know we are going to be taking a pay cut while moving to France from a double income family to a mere stipend.
Our family includes a toddler and a soon to be five year old, I plan on joining my husband a year after he moves.

As an expat we'd probably stay in France for two to three years at most. So I am not very keen on my son going to an all French school.
But while searching online I found most International schools to be quite expensive, is that the really the case ?

Are there Public schools that teach in English?
How does one judge the Private international schools ?
Also, are there any specific benefits(in terms of family school subsidies) offered to Phd students (outside the purview of the university) ?

Appreciate your help, Thanks.