The bottom line is that we have other terms and the Polish Matura would need to be presented in such a way that it would be understandable to educational institutes.
Educational institutions can deal with Polish Matura exam or even 'maturity exam' as bureaucratic literal translations of the kind needed for admission or transfer credit decisions (though 'maturity exam' is a horrible sounding collocation). In everyday usage with educated native speakers of english neither is advised. (I use matura in English with people who know what it is, with people who don't know what it is I say something like 'high school graduation exam' maybe adding that's something like the French Le Bac or German Abitur if I think they might know what those are. "High school leaving exam" is kind of bland but alright in international English maybe (though again Americans who have no such exam might still be puzzled.