Take it with a grain of bias, because I too went to a Christian Brothers school and hated it, but I absolutely adored Sing Street.
It rehashes a lot of things you will have seen before, but if you're a lover of the 80's, alternative music, coming of age stories or even just good cinema, you could do a lot worse than Sing Street.
Final rating:★★★★ - An all round good movie with a little something extra.