Despite the lack of context (country of origin, target audience, etc), and the fact that this is probably in the glossary and if not, it should be, I'll offer a few suggestions. For example, Google translate offers "High School Diploma", which might be good enough if the target audience is the USA (see link below).
However, in Europe, depending on the purpose of the source text, variants such as "baccalaureate certificate/qualification" might be more appropriate. Educational terminologies like these are a can of worms at the best of times.

https://www.linguee.com/english-spanish/translation/baccalau...