First off a high school simulator sounds funny :P. But one suggestion I might have is to "divinity" it up and make a teenage source academy simulator
For the matter at hand:
I'm not overly familiar with the dialog editor in 2 yet, but I didn't find the CompanionRelationUp flag in the story editor at all. I did find it partially but it was for specific origins. So that must work some other way, object script or built into the dialog editor somehow.
So instead of knowing exactly how that works, you can always brute force it in the story editor.
ChangeAttitude(NPC GOES HERE,_Player,50);
So if you had just one item, that was to boost one specific NPC attitude you could just do that and put the specific NPC GUID and specific item GUID in there.
And if it's an item that doesn't "consume" by default you can delete the item in the same statement right after the change attitude part.
If there are multiple items, and multiple companions, then it gets a tad more complicated. In that case you'd need something a little more systemic. Probably not too hard if you're familiar with the scripting. If you're not I can probably give you a rough outline if you can provide more of the particulars.