All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
If the school is a religious school and teaches the Christian sciences and false beliefs – and this is what we understand from your question – then it is not permissible for you to work in this school at all, as Allaah says (what means): {…but do not cooperate in sin and aggression.} [Quran 5:2]
Work there is even more forbidden if this requires serving pork or wearing clothes that do not conform to the Islamic dress code or if it requires forbidden mixing with men, such as being in seclusion with them and so on, as all these are Islamic prohibitions and evils upon evils, and a Muslim woman must avoid this.
Even if it is a public school that teaches worldly sciences, like public schools, and it is only supervised and funded by the Church, then the prohibitions that you mentioned, such as serving pork or wearing immodest dress, are enough to render this job forbidden.
For more benefit, please refer to fatwa 81490 and 83607.
Allaah knows best.