I just finished organizing all of the kid art in my house.  What a great feeling!  I used 9×12 Art Portfolio books by Itoya.  Lila (4 1/2) has 1 book dedicated to her first 2 years of preschool.  Adeline (7) has 1 for each grade (Preschool, K, 1st).  Going forward anything worth keeping will get thrown in their art boxes throughout the year.  At the start of each school year, I will take all of the saved art, school work, writing, awards, etc. and fill a new portfolio book for each child.  The girls were thrilled to go through their books after they were all assembled!  Contact Sorted Nest if you would like help putting something like this together for your kids.