They are interesting, but they are a bit more aggressive for the guppies and they use their sense of smell to find food, and also taste whatever they bump into. I'm not saying that you can't try it (as I have a peaceful Kribensis cichlid with some smaller tetras), but they might be idea bad for the guppies, and the frys (which I think you are trying to get).
I have had success in keeping Neons, Black Phantoms (I'm not sure if they are schoolers), Kribensis (a lone one, as a breeding pair would kill them, which is what happened to the two male guppies in with them), Otos, Cories, Platies (not schoolers, although like to be in groups, like the guppies), Mollies, Kuhli loaches (like company) and yoyo loachs.
To me, it seems like having two schools of 6-8 individuals per school with a school of 5-6 cories would be good... I'm not sure if 2 schools with 10-12 fishes in each school would be good, as you would have 5-6 cories and then also a few guppies (If 10-12 fishes per school is what you mean by "BIGGER schools").
I'm just trying to give you advice on what I think is correct.