I'd disagree. If they are doing a prize a day, they obviously needed many local businesses to support them. Why should a local gun shop be excluded? It's a legal business. No guns would be brought on campus. Any winner could decline a gift they didn't want.
I don't hunt/own a gun myself but was brought up in a family where guns were common. My brother is a champion shooter (targets). It's very a popular hobby - even an Olympic event.
The gun shops around here tend to carry a variety of stock. Certainly guns and ammo, but sometimes hats or clothing or books; other protective items like pepper spray or safety gear. If you win, you don't have to use the certificate. Donate to a group that teaches gun safety. Throw it away. The shop probably sells some gum near the register. Buy $25 worth of gum.
If you stick with the premise that the school should not accept donations from stores that sell guns and accessories, then you also need to exclude Walmart, Sports Authority, Academy and a lot of other places.
My grandson came to me and asked me to support his school (Cheshire Elementary School of Cheshire MA). Of course I was ready and willing with my checkbook open. His school is selling a Cash/Prize Calendar for 10.00 where each day in December a name is pulled and you are awarded the prize or Cash that is listed for that day on the calendar. I read with interest until I got to December 28th. where I saw a $25.00 Gift Certificate to a GUN SHOP!!!!! Am I ever so angry at the person who let this gift certificate go through? As a parent and grandparent I have tried to teach nonviolence to all who walk through my door. To have such a prize on an elementary school fundraiser is totally wrong. I am truly puzzled at an organization that supports the children in the school at making such a poor decision!