Dependent college student

My son is a 21 year old college student and I claim him as a dependent on my tax return.  He has a part time job at a local supermarket.  Does he have to file a separate tax return?  I have not received his W-2 yet, but it should not be more than $10,000 /$11,000 (I don't think).

 

Thank you very much!

RP