This question is one that many parents face once they decide to send their child to private school.
Finding that "perfect fit" is not an easy task - but it's not impossible. For general tips on details to consider, please see: Choosing the right school.
Also, we have a downloadable pdf that outlines steps that a parent should follow in order to gain valuable information for making a sound and informed decision when the time comes to choosing a school. Please see our complete guide: Five Steps to Finding the perfect match
Also, if language is an issue for your particular situation, you should also be mindful to look for schools that have integrated ESL classes.
Good luck with your search!