Yes, we know, High School Musical is incredibly popular. The two TV shows, the movie, even the upcoming movie is already popular.
But it does have to be said that it's not so much the plots of the acting that make it so, it's the music. That's what Disney does so well with its various franchises, after all.
So, just in case you're interested, here's a link to the High School Musical songs.
They're all there, all the ones that made it to the soundtracks, and there's information on who sung them and so on. If you're looking to a guide to the music there it is.