To get started, I bought these pink file boxes from Office Depot. Then, I put 17 hanging file folders in each box...one folder for each year. To save time, I printed these labels from IHeartOrganizing for grades Pre-K through 12th grade. I also wanted a place to organize infant and toddler mementos, so I created labels for 0-12 months, 1 year old, 2 years old, and 3 years.
Due to limited space, I am very selective about the items I put in the box (usually only 3-5 items for each year). I store the memory boxes (with a lid) in each girl's closet. (I also started another file box for each girl...where I store larger mementos, such as their first pair of shoes, a favorite blanket, etc.)
These memory boxes aren't fancy, but they will be easy for me to maintain for the next 18 years. I am excited to (finally) have an organized place for my girls' school papers and personal keepsakes!