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.
Registering and booking appointments for patients to see the doctor is lawful work - Allaah willing. The same applies to registering students in mixed schools. The sharee'ah deems it lawful for the Muslim woman to seek medical treatment at the hands of a male doctor in certain cases; and the same applies to studying in mixed schools. The one working in registering the patients or students is not obliged to investigate the people's situations and find out who has a concession and who does not. There is no harm for the Muslim to work in a place where observing the sharee'ah rulings is predominant. However, if the sharee'ah rulings are not predominantly observed, or if they are not observed at all, as is the case in Western countries, then such work would constitute helping others to commit sin. Allaah, The Exalted, says (what means): {And cooperate in righteousness and piety, but do not cooperate in sin and aggression. And fear Allaah; indeed, Allaah is severe in penalty.} [Quran 5:2]
It should be noted that there is another problem in working in such places, namely exposure to fitnah (temptation) through prohibited intermixing between men and women and looking at women who do not observe the hijab and expose their beauty. In addition, it involves becoming familiar with such sins and prohibitions without forbidding them. The Muslim cannot be safe from such perils in most cases. This poses a threat of temptation to the heart, so one should not work in such a job unless there is a dire need or necessity. Verily, prevention is invaluable. Whoever fears Allaah, He shall safeguard him, and whoever gives up something for the sake of Allaah, He will substitute it with something better. Allaah, The Exalted, says (what means): {...And whoever fears Allaah - He will make for him a way out and will provide for him from where he does not expect.} [Quran 65:2-3]
At any rate, residing in non-Muslim countries abounds in many risks and causes significant hardship, especially with regards to children and fostering their Islamic creed and manners. Therefore, migrating to a Muslim country is Islamically required unless there is a real necessity or need for residing in a non-Muslim country. Please refer to fataawa 179175 and 86405.
Allaah knows best.