I don't want to be a buzzkill here but I think a fixed blade is the better choice for today's twelve year old. It is a sad story but I think it should be considered.
We find ourselves in the world of "zero tolerance" where the tiniest infraction in a school can come real close to ruining a kid's life. When I was in school, being a farmboy among farmboys, every single kid had a pocket knife and he brought it to school, everyday. You knew where a guy carried his knife because his blue jeans wore around it. In those days, I carried a Sodbuster Junior in my back pocket (still got that knife too). Kids had Case, Ka-Bars, some traditional boy scout knives although I never saw a Swiss Army Knife...I thin red may have been un-cool.
Today, having the smallest SAK found on you at school would get you expelled and probably prosecuted...no college, no military, no nothing...sad but true.
Therefore, my vote is for an IZULA or and RC-3 or a HEST for a 12 year old because he is much less likely to forget he's got it when he heads off to school.
A real consideration IMO in this era of PC madness. Plus the kid'll love it!!! Plus plenty of grown men and hunters and outdoorsmen rely on an IZULA everyday. Get him the IZULA kit with all the survival stuff...how cool it that!