Conversation so far:
when was the first year GCE Advanced Level examination took place
The GCE was first introduced in 1951 to replace the Higher Schools Certificate, and final examinations are normally taken in England and Wales at the end of Year 13.
what is year 13 in British schooling
Year Thirteen is an educational year group in schools in England; it is sometimes the thirteenth and final year of compulsory education, or alternatively a year of post-compulsory education.
What other countries have the year thirteen in their education system
Year Thirteen is an educational year group in schools in many countries including England, Wales, Northern Ireland, Australia and New Zealand.

Question: Why in only such few countries
Self-contained rewrite: Why the year thirteen is only in countries like England, Wales, Northern Ireland, Australia and New Zealand have