I am that mom. When readying K's things for school, I really took a good look at what was in her pencil box. K's pencil box is the same purple plastic box that she's used since Kindergarten. Going into third grade, the box still is in excellent shape. I cleared the things from the box, wiped it off and set to refilling it. K had a big handful of pencils in there that were at least 2/3 of the original length, if not longer. She killed the erasers, so I gave them all a good sharpening, recapped them with new cap erasers and breathed new life into those still very usable pencils. Scissors were the same. I just wiped them off and dropped them back in. Her dry erase markers were barely used last year. They have an ink gauge on the side, so we know they have tons of ink. Voila. Reuse! Her pink eraser was completely reusable, too.
As far as new supplies are concerned, new crayons and new glue sticks were a must.
Once again, K will be reusing last years book bag and lunch carrier. Because of defect, they were replaced by LL Bean in the spring. The backpack that was replaced was the very same bag she carried for nearly 5 years. The locker hang loop ripped out, so we replaced the bag with a messenger bag.
She's good with reuse. I'm glad that she's not a kid that requires brand new all the time. It's good for her to use things up and not to just replace because that is what she thinks needs to be done.