Yes, you can claim him. . .
In general, to be a taxpayers qualifying child, a person must satisfy four tests:
Relationship the taxpayers child or stepchild (whether by blood or adoption), foster child, sibling or stepsibling, or a descendant of one of these.
Residence has the same principal residence as the taxpayer for more than half the tax year. Exceptions apply, in certain cases, for children of divorced or separated parents, kidnapped children, temporary absences, and for children who were born or died during the year.
Age must be under the age of 19 at the end of the tax year, or under the age of 24 if a full-time student for at least five months of the year, or be permanently and totally disabled at any time during the year.
Support did not provide more than one-half of his/her own support for the year.
And he not only can, but must, file his own return. I'm not sure being a student has anything to do with the size of his refund, though I could be wrong.