My son's college landlord withheld a large portion of their security deposit to employ a cleaning service,(normal cleaning, not excessive) clean the carpets and repaint the apartment. I thought these were things a landlord was required to do between tenants at hi/her own expense. Please advise.

The landlord is entitled to withhold portions of the security deposit to cover damanges beyond normal wear and tear.

I suspect, if challenged, the landlord's cleaning service will testify that there was damages to the carpets and walls that was beyond normal wear and tear.