Carl
Level 15

After you file

why would the student have to file a tax return?

If the student has "reportable" income then the student is required to file a tax return. it does not matter if the student is claimed as a dependent or not, on another tax return. 

The student's income is reportable if:

 - the student's earned income when added to excess scholarships income exceeds $12,300 or

 - If the student has more than $1,150 of investment income.

Keep in mind that just because the income is reportable, does not mean it's taxable. But those are the reporting requirements.