Same-sex prom kings, cornrows and school rules

I've been following with interest, and some dismay, the coverage of St Pat's decision to prevent boys from taking other boys to the school ball:

- DomPost: "School denies pupil bringing boy to ball"

The School's position was invidious, mean-spirited, unjustified and - I think - unlawful.

Other commitments mean I haven't had the time to analyse the legal position (other than via some short exchanges on the Facebook).  But it's fair to say the question is actually quite tricky for a number of reasons:
- Is the exclusion discriminatory (particularly in the light of the Court of Appeal's plainly erroneous, but binding, position in Quilter on same-sex couples and discrimination on the basis of sexual orientation)?
- Which discrimination norms cover the situation: the Bill of Rights or the Human Rights?  What is the status of an integrated school under there instruments?  To what extent does running a school ball a public function? Do any the HRA exceptions apply?
- If it's indirect discrimination under the HRA, or discrimination under s 19 of the Bill of Rights, is such discrimination justified?
- Does the rule have a legitimate objective (preventing incidents between current boys and old boys or boys from other schools)?  Is the discriminatory rule the best (or a reasonable) way of addressing the problem?
- Could the rule be justified on other grounds, such as religious beliefs (esp in relation to an integrated school)?
- To what extent should a court or supervising body respect the judgement of a governing school board on such matters?
- Is the rule unlawful on common law grounds as the rigid application of a policy?

Anyway, even with these tricky hurdles to navigate, I think the position probably ends up being unlawful. You just have to trust me on that...

But, in lieu of detailed analysis, can I offer up a decision of the High Court of England and Wales from late this week: a case ruling that a school policy preventing boys from wearing cornrows was unlawful:
 
- Guardian: "School's refusal to let boy wear cornrow braids is ruled racial discrimination"
- SG v St Gregory's Catholic Science College [2011] EWHC 1452 (Admin) (17 June 2010)

There's some analogy - I think - between the well-intentioned, but indirectly discriminatory, rules in both cases.

PS I probably should confess that it was a case involving the unlawful application of school rules (not involving me!) that in part led to me being at law school and developing my passion for law: M & R v Syms and the Board of Trustees of Palmerston North Boys High School [2003] NZAR 705...