**WARNING: Intense waves of sarcasm to follow...**
I'd like to propose a few ways to change a Christian school into a secular school (and there is a difference between the two)...
1) If you have chapel services five days a weak; change it to three. If you have it three days a week; change it to one. Too much "church" is a turn-off to unbelievers (not to mention the fact that it could hurt enrollment/finances to require chapel). Finally make chapel optional before being a good steward of the school's finances and doing away with chapel all together. (Remember, do it slowly so no zealous Christians will cause a fuss.)
2) Strive for intellectual and academic excellence to the neglect of the spiritual state of the campus. Certainly you could probably focus on some one's spiritual health and academic performance, but their spiritual state is just another thing to be juggling and the 'academy' has a different function than the church. You are, after all, a college/university!
3) When you advertise on TV, billboards, or secular periodicals make sure you do not mention your Christian foundation. It is a turn-off and you will lose many prospective students that way. (They might find out if they come to your school anyway, so why mention it?). Even if they don't ever realize they attended a Christian school, you've just done a great job of helping them be Christians even though they may not realize it!
4) Lower the standards for your sports teams. If it makes you feel better you can convince yourself that having a winning basketball team will make a better name for Jesus than a mediocre basketball team that lives a holy life.
5) Hire faculty, staff, & administrators that are not Christians. As long as they do their jobs well, who really cares?
6) Consistently raise your tuition so that you are one of the most expensive schools to attend in your state or region. This is a good way to get rid of some of the more religious students who are studying to be preachers (preachers won't be able to afford to go to your school). It is definitely positive if you can prevent ordinary people from the denomination you are a part of to come to your school because of financial hurdles, this takes away from the close minded Christian influence. Plus you can increase your salary and be more prestigious in the academic world with higher tuition rates and more upscale students!
7) Do away with any kind of rules you might have on your campus. Those include curfew, dress code, required chapel attendance, and any other rules students often complain about. You certainly do not want to be viewed as legalistic. If you have any rules and, for denominational reasons, are not able to do away with them, just leave them in print but ignore them.
8) Change your school motto from something like: "Christlike in all we do" to something that uses some Latin and is translated to say something more general like: "We are nice and we like everybody."
9) Take down all crosses and religious imagery from your campus. It was all probably graven images any way. Put up peace signs, lots of posters on what we can do to help the environment, and weekly fliers about how much more important it is to not litter than take the life of an unborn infant.
10) Replace some of the religious requirements (either chapel or some Bible course) with community service (playing hop-scotch with homeless kids or some kind of non-committal activity that pushes toward little to no change is best). It will fool the Christians into believing you are still a part of the Christian church and convince the rest of the world you want to make a difference without "pushing your beliefs" on anyone else.
11) In your Bible, Theology, or religion department (whatever you might call it) hire a Jew, an atheist, and some other professors who are so smart they think they've figured out why Mary really wasn't a virgin. Your students probably need a larger worldview (narrative if you want to talk like a post-modern) than the narrow, exclusivistic worldview of Jesus/Christianity/the Church.
12) Finally, measure your success by how much money your graduates make or how many books they publish. If someone becomes a denominational leader you can take credit for it within the denomination but do not talk about it outside of the church. (You may be able to take credit for sports stars who thought about coming to your school.)
Extra note: If part of a denomination, you may want to continue to tap into the enormous amount of financial resources available from the many lay people who have no earthly idea what is really going on at your school. To do so, talk a lot about what God is doing at your school (even if you have to exaggerate or even make things up). All some lay people care about is whether or not the young people are serving the Lord and living for Him (how short-sighted they must be)!