The Basic Education Certificate Examination, sat at the end of junior high school, usually around age fifteen.
The score that matters is the aggregate: the sum of your best six subjects, including the core ones. Lower is better - aggregate 6 is perfect.
That number, together with the schools you listed as choices, is fed into the Computerised School Selection and Placement System, which decides which senior high school you attend. In a country where the SHS you went to follows you through professional life, this is one of the most consequential exams a Ghanaian sits.
Choosing schools realistically matters as much as the score. Listing only the most competitive schools with a weak aggregate can produce no placement at all.