I agree with the other responses that both are great schools. I think the main difference is the method they use to teach. Covenant uses the classical approach. It is kind of hard to explain and I suggest you search on the web for an indepth explanation but here is one excerpt I found:
What makes classical Christian education so effective? First, it is based on what has been called the trivium. No matter how your child learns, he or she goes through three phases. In grades K-6, students are excellent at memorizing. In grades 7-8, students become more argument-oriented. They are ready to be taught logic and critical thinking. In grades 9-12, students become independent thinkers and communicators particularly concerned with their appearance to others. To this end, classical education teaches them “rhetoric,” the art of speaking, communicating, and writing. The website I got this from is http://www.foundationsacademy.org/about.htm
I have several friend who's kids go to Covenant and they love it. My husband and I plan to send our girls there. (They are only 2 and 4 right now.)
I think all private schools have an open house in January.
Hope this helps.
K. W.