Hi
Usually, I duplicate and turn the field for such goal, to avoid possible data loss. You can do almost the same, by just creating linked field on the right of StudentID and then copy-paste whole field. ( but I guess both ways will not work in your case )
Anyway, when you paste a column of values (or turn column with values to a linked field), each of them seeking match in a primary field of Table 2 and links to the first it find (order not guaranteed). If nothing found, it creates new empty record with value in primary field and links to it.
So, in usual state, IDs shouldn't dissapear, all must be linked, and in Table 2 you should see a group of new records (means IDs of Table 1 that are absent in Table 2). And some unlinked records in Table 2, union of 'absent in Table 1' and 'has duplicate in Table 2, which already used for linking (more lucky)'
BUT, in your case, Table 2 has formula or synced primary field, that can't be overwritten directly, that's why new records can't be auto-created. And therefore, primary field of Table 2 is not a column of StudentIDs (just guessing). That's why they can't be linked.
Linking two tables by non-primary ID is not so hard. Can be done by script extension, or, if you can't code, by simple automation with 'when chkbox is ✔' - 'find' - 'update record (linked field)', or, to avoid wasting automation runs, manually via third temporary table.
Almost forget - you can temporary switch primary field to use necessary data to link, and recently Airtable added it (switch primary field) as function in right-click menu, so it's maybe easier than 3rd table.
In my opinion, the best way is to use IDs according to their purpose, I mean as a primary field.
I hope you will be able to accomplish your goal and get familiar how linking works.
