Good for the school. Sad that it is necessary it has to indicate what should be common courtesy.
Interestingly, when I participated in parents' evenings, as a parent and a teacher, in the industrial midlands, parents arrived in suits, both sexes, and smart casual; the saris were a sight to behold. It was regarded as an event.
Move to the leafy 'shires'; the standard of dress was low, staff and parents alike, although the school uniform rule was closely observed. Some staff indicating their resentment at being there; the parents, indicating a faint contempt for the world of education. The mother who annoyed me most was the one who arrived straight from mucking out the horses, and said I wouldn't mind her walking across my carpeted classroom in her dung- covered wellies, would I. I wasn't brave enough to say, leave them at the door, and the odour lingered throughout the evening.