I have been a professional guitarist most of my adult life and I also hold a degree in Music Education. I am unique in that I have inside knowledge of both worlds. 

Here are some of my answers to the question above:

1) Guitar is primarily not an ensemble instrument, it is an accompaniment or solo instrument. When you try to put a guitar into an ensemble setting, you are trying to fit a square peg in a round hole. It just doesn't have much relevance to a student who started guitar because they wanted to be a GUITAR PLAYER.
2) Not much beyond classical literature and a handful of method books use standard notation to notate music for the guitar. When they do use standard notation, it is full of additional notation regarding fingerings, strings and right hand plucking... Most often, standard notation is accompanied by guitar specific notation such as tablature or chord grids. If you want to teach guitar, you must understand Tablature, Chord Grids and be willing to accept playing by ear. 
3) Guitar players often feel shame or feel intimidated because they don't read music (see #2) and so they avoid the school music programs.
4) Most popular music is generally written by ear and THEN notated, notation is an afterthought. While most Classical and Band literature starts with a composer and a score, most popular music is developed without notation. This explains a great deal about why band directors can't understand why guitar players don't read standard notation and why guitar players don't see the value in learning to read standard notation.
5) Guitars are not in a marching band and often school music programs are an extension of the athletic program.
6) Band directors and therefore schools, don't win and awards for having a high level of student participation or creativity in their music program, they win awards for students performing well at band, orchestra and choir competitions.
 
Share your thoughts and stay tuned for my next blog when I answer the question "why should band directors and guitar players connect?"

I am starting a blog, I hope your subscribe! People are always asking me "how can I be a successful guitar player?" In response, I have created my "Top 10 lessons every guitar player should learn to be successful" list. 

1) Practice, and when you are done with that, practice some more!
2) Remember very few people call you because you play really loud and have a big amp.
3) When you do get a gig, arrive on time and dress properly. 
4) Don't just play, LISTEN.
5) Carry spare strings, cables, guitars etc. 
6) Return phone calls and messages.
7) Carry business cards.
8) Save the partying until after the show.
9) Start a website.
10) Always be positive, humble and say "Thank you."