mamola - welcome!!
Beware, WC ("wet canvas" for newbies) is addictive! This is a wonderful resource!
I'm at home and my portfolio is in my classroom - I will tell you EXACTLY what's in it when I get there tomorrow! - i came out of an art education program last year w/all level certification in Texas, and I can tell you what principals, in broad general terms, are looking for.
To get you started, I have (not in this order - I'll give that to you tomorrow) - your resume, art education philosophy, examples of students' work (digital or regular photos in nice photo sleeves) w/ the lesson plans you used for that work, examples of your own work (photos), and the TEKS for each grade level - since that's a big deal. If your lesson plans are cross-curricular, all the better for you! If not, write some!! Only include lesson plans for jobs you are interviewing for - I would pull out my high school plans when I went on elementary interviews.
When I get to school tomorrow, I will PM you the exact contents. Meanwhile, check out this website: http://finearts.esc20.net
This is the Region 20 (San Antonio area) website for arts education. You will find many resources on links for lesson plans, assessment, the TEKS by grade level, etc. VERY helpful - I use it almost daily.
Good luck on finishing up school - and I'll get you the rest of the info Wed.