For most students I would suggest a YYF Whip. They’re responsive yoyos that are cheap but are actually also pretty decent but can definitely be bought in bulk without putting too much of a strain on the wallet. They are also c bearing compatible as the initial bearing is a slim-c.
For kids that really want to get into it I would secretly set aside either a few Duncan Big Funs, C3 Speedaholic XX (in this case make sure to tell them about the fact that these come unresponsive in most models so suggest they slap the bearing from the Whip in there to start with), or YYF Arrows. These ones are still relatively cheap but are good yoyos that will actually serve someone wanting to learn quite well.