We organized my 8 year old’s papers and special box which holds all her small treasures and toys. She started with a lot but was able to whittle it down to a manageable amount.
Start by dividing the papers from the toys. Then take each group and evaluate them separately. With papers, I like to set 6 of them out and have the child pick their favorite 3. Then keep doing that over and over until they have gotten down to a manageable number of papers. I like to only keep what will fit in a folder.
With toys, I help them sort everything into categories. Then we go through each category and see if she wants to ‘keep,’ ‘somewhere else,’ or ‘donate’ each item. Often if kids want something stored somewhere else it’s the first step in letting go of the attachment. Gently remind them that they will only be able to keep what fits in their ‘special box’ so if it doesn’t fit then the need to let go of something else.
By breaking it into chunks and focusing on what your child loves the most you can help them figure out their true priorities.