Will cories school?

Corys stick to their own species for the most part, in terms of shoaling. Obviously it won't bother them to be mixed up, but its best to keep a good number of each species. Always exceptions though.

I have four diff kinds and they are small to large and they all school except one loaner panda Cory

You could also just add some more leopard cories to the one tank.

I have many Weitzmani corys and 2 panda corys in a 29 gal. I added the pandas as they were the last of their kind and I did not want to get any more of them. They look similar in color so that may be why but they mingle with the Weitzmanis like they are one of them. This may not always work out but Weitzmani and panda corys will school together.

My pygmy cories shoal with otos when looking for food, which is typically in the morning.

Ive not seen my different cories school together. They might be swimming near each other occasionally, but never like they do with conspecifics.

Corydoras are very social when it comes to other species of Cories

My pygmies not only shoal, but they sometimes play follow the leader...

Tommy

I have 2 species of cories. Leopard & some other kind that looks like a masked but with spots(LFS had them mislabeled). They will school by themselves(separate species) 75% of the time but 25% of the time they will all school together.