All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
First of all, if you can enroll your children in Islamic schools and avoid Christian schools, then it is incumbent on you to do so. If this is not possible because there are no Islamic schools available, then you should know that one of the principles established by the Sharee‘ah states that: “The lesser of the two evils should be endured in order to ward off the graver one.” Shaykhul-Islam Ibn Taymiyyah said in Majmoo‘ Al-Fataawa: “The Islamic Sharee‘ah endorses the realization and accomplishment of interests as well as the elimination and minimization of evils. It gives precedence to realizing the greater of two interests or enduring the lesser of two evils and missing out on the lesser of two interests to realize the greater one and enduring the lesser of two evils to ward off the graver one.” [End of quote] He also said: “It is essential to realize interests and accomplish them and to eliminate evils and reduce them. In the event of a conflict, realizing the greater of two interests or enduring the lesser of two evils is the action opted for by the Sharee‘ah in this regard.” [End of quote] He also said: “A wise person is he who gives precedence to realizing the greater of two interests and warding off the graver of two evils.” [End of quote]
That said, you should consider the evils that would result from enrolling your children in those schools and compare between them. If you believe that enrolling them in religious (Christian) schools is the lesser of the two evils compared to enrolling them in secular schools and you feel safe that the soundness of the children’s creed is immune to deviation, then there is nothing wrong with enrolling them in such schools.
There is no doubt that the Sharee‘ah commands obliterating the cross from the school’s slogan. If it can be obliterated, even in an unnoticed manner, it must be done. If this is not possible, then the evil of leaving the cross in the slogan unchanged while denouncing it with the heart should be endured as long as it is lesser than the evil incurred by enrolling them in secular schools, pursuant to the aforementioned principle: “The lesser of the two evils should be endured in order to ward off the graver one.”
Allah Knows best.