should my friend go into gcses or a-levels?

i don't think that this is a typical question on here, but still, she asked me for help and i'm asking for a friend. my younger friend is currently 15 years old and she's recently moved to spain from poland, so she's in 4° eso. she completed 8 years of education in poland and being in spain without knowing the language has been really hard for her and she's been thinking about changing to a british homeschooled programme at the start of 2027/28 academic year. her 16th birthday will be in the start of the academic year. does she go into the final year of gcses or the first year of a-levels?