Question: do muggle parents know about hogwarts?
Answer: In Goblet of Fire, Hermione explains that Muggles cannot see Hogwarts: '[Hogwarts is] bewitched,' said Hermione. 'If a Muggle looks at it, all they see is a mouldering old ruin with a sign over the entrance saying DANGER, DO NOT ENTER, UNSAFE. ... It's not against the rules for Hogwarts parents to visit their child(ren).