For primary school if you want to start your child in the Greek state school you will need official translation of birth certificate and also a certificate from you local GP that your child is fully enoculated also certification from the English school stating what year the child has completed.

For secondary school and up the same paperwork will be required.

Primary school intergration depending on the area will do their best to help your child learn Greek and then move her/him to the relevant year. Secondary and high school do not do this. They basically give the pupil a year's grace to learn the language and then get on with it; otherwise, they fail the year.

If you are moving to Athens then there is a choice of foreign schools that have English language and UK curriculum or USA curriculum.

For your 15 year old, this is a very crucial time and really the child should not be changing school let alone language and curriculum. Naturally if your children speak fluent Greek, you will have no worries.