Best independent school with little religious affiliation in St. Louis? Urgent!?

My daughter will be starting high school and the school she recently went to was horrid, so we are willing to move. She will be starting 9th grade and we need a school that will offer 9 through 12 grade. I don't mind a private school, but we aren't really religious and don't want her whole day to be centered around it. I would really appreciate replies quickly. Thanks.