Whilst I acknowledge there was a plebiscite held which resulted in legalisation of same sex marriages, I don't believe this resulted in any compulsion for religious schools to endorse anything other than what the Bible teaches.
It is completely valid in my opinion for the school principal to take a stand stipulating that lesbianism should not be normalised at an official school event, their Annual Formal.
Separation of church and state is a fine principle. It gets murky when religious schools accept state financing, but I bet Islamic schools are nit criticised for upholding their faith tenets on this issue.
