Although the beaming smiles on the posters of Choir Boy might suggest a chipper coming-of-age tale, this impression is immediately shattered by the play’s opening sequence: five boys, musical-poised, singing and dancing in step to the gospel hymn ‘Trust and Obey’, before one turns on another with a foul homophobic and racial slur unlike anything heard in recent theatre.

At first this seems like a shock tactic – and the audience are certainly awed – but after the dust settles the complexity of this play on the black, gay experience gradually becomes clear.

Written by Tarell Alvin McCraney, whose Academy Award-winning script of Moonlight covers similar subject matter, and performed here at Stratford East, which has a proven track record of ground-breaking theatre, Choir Boy is well-positioned to approach this theme with nuance and power.

It does so by intersecting homosexuality with the Spiritual tradition, a distinctly African-American form of Christian music, and one that is upheld by the five-boy choir of Charles R. Drew Prep School for Boys.

Pharus (Terrique Jarrett), the recipient of the opening abuse, has been made choir lead, and urges the group to liberate themselves from the strictness of the Spirituals by adding their own melodies: “We sing our melodies our way. That’s resistance.” He is contested by Bobby (Rabi Konde), the culprit of the slur who drives the homophobia harder as he defends the tradition and expresses his outrage at the insinuation that the Spirituals are not authentic. Bobby is evidently frightened by the undertones of this change.

Where the play excels is dramatising Pharus’ search for acceptance in a world trying to suppress him, not least in the exhortations of Headmaster Marrow (Daon Broni), who tries to inculcate Pharus and the other choir boys in an elite, Spartan-like discipline, even when he senses there is discord buried underneath: “There are things you can’t control. But you can control your presentation.”

Marrow schedules their phone calls home, gives them a warrior gesture, and arranges an extra class with Mr Pendleton (Martin Turner) - “a class that will help you think outside the box.” Though these scenes are not always convincing, they do shed light on the hypocrisies of the liberal education system that aims to challenge thinking while also condescending and confining black students. Pendleton criticises a paper on slavery for “taking it too personally”.

Mr Pendleton is the only white character in the play, and this and the absence of any other white students makes the unwavering focus on boys feel purposefully suffocating.

Following the interval there is a shower room set revealed behind the curtain, and it’s here that the play reaches its psychological depth. There are scenes in this setting that challenge the audience to confront homosexuality on stage, and the reactions to certain moments, which confused comedy with sincerity, show that there is still some awkwardness among British audiences.

There are also more solo performances in this half, and the players are far more liberated and affecting when singing along than in a group. David (played marvellously by Michael Ahomka-Lindsay) delivers the defining musical moment of the play, and also emerges between the conflict of Pharus and Bobby as the most complex character, whose impassioned declaration of the Psalm “we are fearfully and marvellously made” is revealed to have deeper proportions than we initially understand.

It is this line, ultimately, which is the symbol of the play, and though the play ends unresolved with Bobby becoming choir lead, singing the opening gospel in straight and narrow fashion, his commitment to tradition has a tragic resonance: “Trust and obey. For there’s no other way to be happy.”