List of users and associated data

[Barry Levine]

I have a need for a stack which will be used for a user login. The 
target audience is children so they will have to select their name from 
a list. There will be a method for an admin (teacher or parent) to 
add/delete a username from the list. While I will need to keep track of 
various data (last login, tests taken, scores for each test), the user 
should only see his/her name.

My thoughts are to use a separate stack (so I can modify/save the data 
residing in this stack) and, in the stack, have an invisible field 
holding a comma-delimited list of the data (which is programmatically 
updated when a user completes a test) -and- a visible list field that I 
re-populate with the user names whenever a user is added/deleted.

It is possible that the list of users will be as many as 50. I am 
avoiding any kind of external DB for simplicity's sake.

What are the listas' thoughts on this matter?

Thanks,
Barry