Ion Auth - Lightweight Auth System based on Redux Auth 2

[eluser]digital_frog[/eluser]
I'm not sure if there is a built in way to do this, but is it possible to look up the ID of a user you are creating from a different account? I have my teacher data and my student data separate from the user data table, so when I create their accounts, I need to create their rows in those extra tables as well. I created those extra data tables by using the auto-incrementing ID from the users table, so when I create a new user it's the only piece of information that I don't supply ion_auth for registration. Should I create a new function to look up the id based off of the other user's data or is there something built in for that?