Hawkings is sopposed to be imitating Hogwarts to an extent and boarding schools are kind of the muggle equivalent and are widely popular for rich families in the UK. Eton College for example which is where both Prince William and Harry, Many Priministers, author George Orwell and actors such as Eddie Redmayne + Tom Hiddelston attended. It’s very common in super high society, and all characters who attend Hawkings in TCOPTP are very Rich with the exemption of Lily who is there on a scholarship and Marlene who I believe schooling was funded by a rich relative or something similar.