Tell me you haven't read harry potter without saying you haven't read harry potter.

1. Purebloods are arrogant and prideful even the ones that don't believe in bloodline superiority treat muggles as lesser, so obviously muggle studies are out dated and generally deemed unnecessary, even arthur weasely has no real clue about anything muggle.

2. All muggles have an education, but just like normal rich kids, purebloods also have a leg up when it comes to education, they get tutors to teach the knowledge needed to pursue their magical education. Just because it wasnt written word for word doesn't mean that common sense should be ruled out