Mostly all French schools in Paris teach the same things the same way, but it is always best to understand what you need more. While a small class would mean more personal attention from a trainer, it would also mean less peer help. Also try and find out the type of class you are joining. Where a basic French course would introduce you to the language, an intermediate and advanced course would help to achieve fluency in the French language. Understand the fact that French is one of those intricate languages that can’t be convincingly translated to English or for that matter, any language- French has its own identity. So, if you are planning to learn French by translating English words, it won’t work.
Learning French from a person who is fluent in your language too is a very good method to ensure that the student to teacher communication is easy. What you need is a teacher who can communicate the intricacies of the French language to you in your language. That will make you understand step by step how to reach for perfection in the language. French schools in Paris generally cater to all personalised needs of students and being a French speaking population, practising and learning the language is the best way to get hold of it.