There is no "school" that I'm aware of. A lot of what I use for PICBasic I got in high school. (I took an QBasic course) The other way to go is a book (or two), there are a number of good books out there to learn from.

That being said the user manual says it best when it states that progarmming is an "art." For me it was a lot of practice and asking good questions. My early programs were rough but they got the job done, and best of all I learned from doing.