Any tips for telling my boss I'm applying for law school?

I'm not sure if this will elicit a response, but a google search didn't pull up any results for "how to tell my boss I'm applying for law school," so I might as well give this forum a shot.

In brief, my situation is this:

Since graduating from college two years ago, I've worked as an Assistant to an in-house attorney. The problem is that I love certain parts of my job too much, specifically, the parts that require legal skills.

Now I'm applying for law school, and I'm trying to figure out how and when to broach this subject with my boss. I'm applying to one night program, so there is a small chance that I could work and go to school at the same time. But most likely I will have to quit my job. So, should I talk to him about law school now or wait until after I get in?

The case for approaching him now:

1. I've always been straightfoward with previous employers about my long-term plans, and they seemed to really appreciated it.

2. My boss could write a killer letter of recommendation.

The case for waiting:

1. I'm worried that with the current economic situation, my Company will be looking to lay-off more people in the near future. Even though it's been suggested that my job is secure, if they think I'm leaving in a year, I'm a little worried I'd be the next to go.

2. I'm not 100% sure I'm going to law school next year (it may not work out financially), and I don't want to stress out my boss unnecessarily.

Any suggestions?