IF you were travelling with 4 pieces of luggage and had 13 pairs in each case along with receipts, IF when you were to go through the nothing to declare channel and were stopped and 1 of the bags were checked 13 pairs of shoes for a well shod lady or gentleman is not REALLY excessive.

If you had an arrangement with the school or charity that you are supporting they could apply for a tax exemption
I once arranged 5 barrels transported by Air Jamaica from the U:K( no charge) for The Windsors Girls Home in St Ann.
The Superintendent Ms Black made all the arrangement for customs and pick up and the Home did not have to pay any taxes on the items.
There are other ways to support charities but God Bless you for bringing down the shoes. Hope you don't get hit with high tax.

B