Oh my goodness...I've found my people! ;) I was an elementary school teacher before I became a SAHM and honestly, I get all sweaty and flustered when back to school sales start...I LOVE IT! Just today I started buying fun little things in the aisle at Target and I know it will only grow bigger as the weeks pass! In fact, if anyone is interested Target had these adorable little packs of crayons for $0.99 that were themed colors...like princess colors, pirate colors, outer space, neons, etc. Adorable! I just bought 2 packs as a surprise for my kids on our road trip next week!
Anyway, I digress (see how easy it when I talk about school supplies!) I do hoard them as well and my kids aren't even in school. They are 2 and 4 but I keep a healthy supply of crayons b/c we go through them quickly and I buy markers, glue, and other fun stuff (see above ;) that I find as I go. The best part about my kids not being in school yet is that a lot of the supplies go even cheaper after school begins b/c they just want to get rid of them! So I can get notebooks and other random goodies for even less!
And I think it's great you donate supplies. I taught in an area that was incredibly impoverished and as a classroom teacher I was always so thankful when someone else had donated extras. Don't forgot about tissue, hand sanitizer and ziplocks either...those were always appreciated as well. And sending in a new round of stuff after Christmas break would be a big help as well. Things start to get lost, broken and used up and old, so don't forget about mid year!