It is a really good show. It has very strong characters and good role models. For example, Kurt Hummel is an openly gay student. He is always bullied, but he refuses to become anyone other than who he is. Or Emma Pillsbury, the guidance counselor with OCD, cares very deeply about the students and helps them solve their problems while overcoming her own issues with OCD. However, there is some sexual content. For example, one character is pregnant, 3 characters are openly promiscuous (Brittany, Santana and Puck), and sex is frequently discussed, usually in a casual way between the students. There is also some slightly tense moments concerning bullying. Dave Karofsky, a football player, constantly tortures Kurt by bullying him, slamming him against the lockers or simply 'terrifying me,' as Kurt put it in the show. The bullying isn't scary like a horror movie or anything, but it can be quite emotional to watch, especially watching Kurt's reaction and how it makes him and his friends and family feel. There is also some bullying just for comic relief, too. A running joke through the series is that the Glee Club kids get 'slushied' by the jocks, meaning that the jocks take a slushie and basically throw it in their faces, a 'slushie facial', which is actually quite funny. I do believe this show is appropriate for the most part. Just know your kids and know what they can handle, but I think this is fine for most kids 11 and up.
What other families should know
Great role models
Too much sex
Too much swearing