I'm a 4th grade (9- and 10-year-olds) teacher, but aside from making a few of my characters teachers, I don't use much from my job in my writing. If I wrote more child characters, I probably would.
I'm far from an expert, but I have some background in music from years of taking piano lessons, playing the clarinet in band, and singing in choir, and that has come in handy for scenes when the guys are singing or playing music. I can read music and have a pretty solid knowledge of musical terminology and structure. I don't know much about the music business, though, besides what I've learned just from years of being a fan, so I find that aspect of it a lot harder to write.
I don't really have any other big hobbies besides writing, but I've been interested in medical stuff since I was kid, and that obviously comes into play in my stories a lot. I don't have much real life experience to draw on, but I have taken anatomy classes, watched a lot of medical shows on TV, read a lot of books, and done a lot of research on that kind of stuff so I can use it in my writing.