On the uniform aspect, full honestly ever since starting Hogwarts Legacy [thanks 80% off key code from 3rd party site] Ive filled in the gaps of uniforms from the outfits that they have on there. If anyone wants me to compile links just lmk.

Victorian children in general, from what I've researched, really were just dressed like adults but with simpler and less complicated themes to their outfits.

From this link:

Quote:In Victorian times, children’s hairstyles were a miniature reflection of adult fashion, albeit simpler. Girls typically had long hair, styled in soft, gentle curls or simple braids. They might often have ribbons or small flowers in their hair. The flowers would often be real but sometimes made of silk, particularly in the cold months when flowers were out of season.

Young boys, usually had their hair kept long and in curls until they reached a certain age, known as the ‘breeching age,’. At this stage of childhood they would start to wear trousers and their hair would be cut shorter. This grooming marked their passage towards a more ‘masculine’ appearance.

Like others have said, I think we can also safely say that the Wizarding World tradition of a wix child coming of age at 17 would make sense to start with more adult styles.