English Bulldog - Obedience class for aggression

Question
My 2 year old female english bulldog is "selectively aggressive" towards just some people - some people walk in my door (usually dog lovers) and she's perfectly fine - but with others (usually young males for some reason and/or people who aren't "dog people") she runs, growls, and jumps - and it definitely scares people - I just don't know when it's going to happen.  (she is spayed by the way).  I know your advice is usually to take them to obedience class - how do I know if a particular obedience or training class is a "good" one before I spend a lot of money (or worse, let people who aren't doing it properly affect my dog).  Thanks - Amy

Answer
This is territorial behavior in your home. For whatever reason, the dog feels you need to be "protected" from certain people.

Do some research on trainers in your area. See if they have experience with behavior modification techinques. Ask for references from previous clients.

This should have been done when the dog was a puppy. Too often people think that Bulldogs don't need obedience work because they're not going anywhere with them. Then they end up with an antisocial dog who exhibits unwarranted territorial behavior such as you're experiencing right now.  This isn't impossible to resolve, but it will take some effort on your part to not only find someone with expertise on this matter, but who will also train you to train your dog.