If you want to work with children you need to take courses like child psychology, social sciences etc. You should talk to the people who are already working with the children and you will get a fair idea on how to do this. You can even take tips from your instructor as well.
It depends on what options are open to you different schools offer different things some schools may offer a childcare course I would def speak to your tutor to guide you or perhaps a career advisor,I think that Drama would be a good option as well and it is very enjoyable, its not easy but very beneficial for a wide range of different career. I would also suggest a cooking course as I think it is useful to know how to cook properly and different ideas hygene etc which you will need when looking after children.
I would take drama because then it would make it enjoyable and you could also take a basic one like child development.
If you want to work with children you should take child psychology at advance level or a BTEC/NVQ in child care at college- if you are planning on becoming a nursery teacher.