Christian School Teachers-- held to a higher standard?

I recently read an article about a private Christian school teacher who was fired for having premarital sex. She was pregnant at the time.

Apparently this is not an uncommon issue. Many teachers are forced to sign contracts at religious schools that condemn premarital sex, and sometimes even extend to drinking in public and homosexuality.

The legal parameters are complicated in these cases. While the teacher might have violated the contract, there is some question as to whether the school fired her because they didn't want to pay her during maternity leave. Besides this, there is an uncomfortable overlap of church and state, where a person's livelihood can legally be deprived for a religious reason. This reminds me of religious objections to providing birth control coverage to employees; where does the power of the state overturn the autonomy of a religious organization?