One should try to find an equivalent in the target system, and in the case of the UK that is GCE A Level, but I would not translate it like that.

If the translation were for the US, "High School Diploma" would be ideal. However, this term is not used in the UK, and if it were used here it would imply that the person had studied in the US. Similarly, "School Leaving Certificate" or "Leaving Cert" is the Irish equivalent.

The equivalent British qualification would be A Levels, but to put this would give the wrong impression, since A Levels involve a much narrower subject range. It is not GCSE, which is taken normally at 16 and in equivalent to a stage before the Bachillerato. GCSEs do not qualify you for higher education; you have to take a further two years of study and get A Levels.

These further two years of study are traditionally called Sixth Form, for which the modern British jargon is "Key Stage 5", but again these term are very specific to Britain, and in any case they denote a stage of secondary education, not the resulting qualification. They are not suitable here.

I suggest Baccalaureate as an accurate term which is well known in the UK. An increasing number of students in the UK are now taking the International Baccaulearate (IB) as an alternative to A Levels, and this is generally accepted now for university entrance. Referring to the Bachillerato in Spanish-speaking countries or the French Baccalauréat as a Baccalaureate is perfectly standard practice, and I think it is the best option here.

If it refers to the actual certificate or diploma, you would say "Baccalaureate certificate"; if it is the qualification itself, "Baccaleurate" alone.


--------------------------------------------------
Note added at 41 mins (2011-11-25 09:47:44 GMT)
--------------------------------------------------

("Baccalaureate", not "Baccaleurate", in the last line.)