I'm reading several different possibilities in your post.
1. Part-time education
There are several types:
1. Continued education which is directly related to your job and could help you get a more highly paid position.
2. Continued education which is incidentally related to your job, and will only help you personally to do a better job, thus enabling you to become more useful to your employer and potentially gaining a raise.
3. Continued education which is unrelated to your job, and will only help you on a personal basis. I've kind of ruled this one out because you said "one can always learn more about their field."
Whatever the case, I would encourage you to be open and honest about your education. Don't hide the fact that you're going for further education. On the other hand, don't go out of your way to tell your boss, your co-workers, etc. Tell them, but don't make a big point of making sure everyone knows. (Boss included)
2. Full-time education
If you are quitting your job, regardless what you are planning on studying, definitely talk to your boss about it. Work out with him/her when you will be able to leave so that you have sufficient time to prepare for the entry to the scholastic year, but so that you can get done any projects that (s)he has for you to get done.
From the way your post reads, I'm guessing that your education falls into the category of part-time education that either directly or indirectly relates to your job. It also sounds from the reading of your post that your goal is not "money, money, money" or a more prestigious position; it sounds like your goal is quality work.
Edit: per edits on your post, I see that this is basically the case. :)
If this is the case, I would recommend not hiding the fact that you're furthering your education: treat it as you would any other similar news. Don't go around making sure your boss and all your co-workers know, but be open and let them know.