Column Reference Question

[James_Brennan]

I am building an attendance app for different Clubs/Activities at my school. I would like the app to take in two data points from a form. 

1. Student ID
2. Teacher/Sponsor of Clubs email

I would like the for to only show a field to acquire ID#'s from students, and all other data is gathered from referenced tables. 

I can achieve most of this, but I am not sure how to make one tweak. I would like to make the Student ID field so students can type their ID numbers. Because the ID column is a Ref, AppSheet is making it a dropdown field in my form. 

How do I allow users/students the ability to type their ID#?

thanks!