It depends. If your son gets paid less than $4,000 then he isn't required to file an Alabama income tax return.
If he is paid more than $4,000, then yes, he has to file and pay Alabama taxes on the income as there is no credit for taxes paid to Tennessee as there is no income tax in TN.
There is no form that needs to be filed for TN.
Do I Have to File An Alabama Tax Return?