I view having a teacher as very handy in a lot of ways, obviously they can provide guidance, direction, and homework (homework being their least significant thing) but they are also handy when you suddenly realize you want to know why a D chord is a D chord or what the heck that F# is doing there. I imagine that you might have a jamming partner at least during your lessons a lot of the time and that's always handy to have I'd think... that said I haven't gotten lessons yet, I've been thinking about it for quite some time but other things are more important to me right now and the internet contains so much information that you can learn a great deal on your own on the cheap, I will say that I'd probably be the greatest guitarist ever by now if I had taken lessons, but teaching myself I'm slowly creeping towards general competence (my original goal anyway).
On the other hand, I was talking to some people who have been in school band for years... who know nothing of music theory, and I mean pretty much nothing, they memorize how to play specific pieces on the instrument they have, they have no transferable skills, they don't even know how to read sheet music... these are the things I'd expect to come out of band, I hope that's not typical of schools and is just an example of a particularly bad teacher at this one school. When you are paying someone good money for lessons you should definitely feel free to ask them what and why and get a reasonable answer, my guess is whoever is giving you lessons would have an easier time too knowing what you want out of them.
