Provided you can show that an institution within the UK issued your certificate of attendance, you can get an apostille for it – no matter what language it was issued in.
However, the FCDO will only accept certificates of attendance in a foreign language if they have been notarised by a public notary or certified by a solicitor.
If you are going to present your apostilled certificate of attendance overseas, you should check whether a certified translation in the language of your destination country is also required.
In England, it is unusual for a certificate of attendance to be in any language other than English. Occasionally a UK language school may issue a certificate of attendance in both the language taught and in English.
Scotland has three official languages: English, Scottish Gaelic, and Scots (sometimes called Doric). In Northern Ireland, the two official languages are English and Irish (sometimes called Irish Gaelic to distinguish it from Scottish Gaelic).
Ulster Scots is also recognised as a minority language in Northern Ireland. The two official languages in Wales are Welsh and English. Therefore, in these countries, your attendance certificate may well be in one or more of these languages.
It is possible, therefore, that you may need an apostille for a certificate of attendance issued in the UK in any one of the above languages. This is especially true if it is a certificate of attendance at a course teaching one of those languages.
Because the UK is now a multicultural society with numerous different ethnicities and languages, you may also have a certificate of attendance issued by a faith school, college, or other similar institution in the UK.
For example, British Muslims who wish to travel to Saudi Arabia for Hajj or Umrah may have certificates of attendance at religious or Arabic language courses.
No apostille can be issued for these certificates unless they have been notarised by an Arabic-speaking notary public or certified by an Arabic-speaking solicitor in the UK (or an Arab British Chamber of Commerce (ABCC) official).
These certificates of attendance, which are very useful for travel in Saudi Arabia, are usually written in Arabic. Provided they have been issued in the UK and duly notarised or solicitor-certified by a suitably qualified legal practitioner, they can be apostilled by the FCDO.