Yes, if his $15,000 income is from wages, he gets the full $12,400 standard deduction.
A dependent's standard deduction is the greater of $1100 or his earned income +$350, but not more than $12,400.
You may be thinking of the pre 2018 tax law, when a dependent was not allowed his $4000+/- "exemption" deduction.
With the tax law change, effective 2018, most students will get the same refund whether they claim themselves or not. The personal exemption has been eliminated and the standard deduction increased.
