It's a crazy thing that your going to college would be considered bad news.
Is the college you plan on attending nearby so you could live at home if your parents are favorable or would you have to move away anyway?
Are you certain you'd be kicked out if you went to college?
Why can't you attend college and not mention ending the JW thing just yet. Let them get used to the idea of college and then gradually fade away sometime in the future.
Perhaps you could sit them down and have the following conversation:
You: Dad...Mom, play along with me here but can you give me 3 examples of things that no parent ever wants to hear about their kid?
Your Parents: No parent wants to hear their child is sick, or they've been in an accident or they are in trouble with the law.
You: What about if they heard their child had been accepted into college?
Parents: Well...no, that wouldn't exactly be bad news....why are you asking us this?
You: Well it occurred to me that even though parents all over the world are overjoyed when their kids go on to higher education, it might come as bad news to you, if I were to tell you I got accepted into a college.
Then take the conversation from there, hopefully you'll have put things into perspective for them.