As far as I know, the Hungarian education system is quite different from that of any English-speaking country, so there may not be an exact translation.
My suggestion is: mock final exam(s).
In British English, a mock exam is an exam which serves chiefly as practice for future exams (Wiktionary definition). Érettségi is indeed an adjective, but it's used as a noun, a shortened form of érettségi vizsga (lit. maturation exam; érett = mature), taken when finishing secondary education.
"Kis" means "small/little".