Yes. They have their own agenda.
We don't live in a vacuum, and people are influenced by all sorts of things - peer pressure, TV, radio, social media, by people in authority etc.
Those people promoting individuality need to read the room. In many cases it is brilliant, but in many cases it is just inappropriate for the occasion.
All the OP needs to do is ask the school, not mumsnet. Although, judging from the reaction on here, I think she realises by now that she will get a similar reaction from other parents in RL.