I am a teacher and although I didn't have my ostomy until just this year, I think she will be ok. Yes, her dexterity is going to make it hard for her to empty at this age, but it is good that you are teaching her, so she can at least try. I don't know what kind of school you are going to be at, but I feel like they'd be ok with you coming in. However, the nurse may be ok with that as well. As a teacher, I would be ok with whatever accomodations that she needed, and if you are taking her to a public school, they will have to accomodate her, so no worries there.
My biggest piece of advice for you would be the same thing I'd tell any parent of a child of any age who had an ostomy: make sure she is confident with what she has, and do whatever you can to educate her and don't let her feel like it is a bad thing. I'm sure that you've already thought of this and I'm sure you've already laid the groundwork here; I just thought it was worth mentioning. If she's happy emotionally she'll be fine physically and be able to deal with any mishaps. She just needs to be able to explain to her classmates/friends if they should ever ask, in a way that makes it ok. Most kids are very accepting if something is presented in a matter-of-fact way. If she presents it in a way that is shameful, they will regard it that way too.
Stephanie, 29 years old
March 2000-Diagnosed Crohn's Colitis
(Tried every drug imaginable, but lived 10 years with daily diarrhea)
March 18, 2010-Total Proctocolectomy and Permanent Ileostomy! :)
(Now med free, 4 subsequent procedures to correct blockages at stoma site)
Stoma named Zoe...She's my best bud!! :)