I was playing a dwarven cleric who could summon small elementals, and started summoning earth elementals 10' (for instance) above enemies to basically combine my monster summoning with a crushing attack. I was fine with the elements taking falling damage. The DM allowed it, but is it allowed by rules? It seems to be, but I can't find anywhere that specifically addresses this tactic, which could become extremely abusive as my elementals get bigger, doing more damage and caring less about the damage done to them by the fall. It's already like getting a spell and an attack for one action...
A creature or object brought into being or transported to your location by a conjuration spell cannot appear [...] floating in an empty space.
This line was almost-certainly added specifically to eliminate the tactic you’re describing.