The C-corp can add the student loan payments to the president's salary, where it will be subject to tax withholding, social security, medicare, unemployment tax, and all other good things. Just as if it was an increase in salary or a bonus.
What you are really asking (I think) is can the repayment be tax-free? For this, see publication 15-B on fringe benefits.
https://www.irs.gov/publications/p15b
Any educational assistance program must be in writing and must not discriminate. For example, it might apply to all full-time employees, or all full time employees with more than 2 years of service. But it can't be constructed so that the person you want to help just happens to be the only person who qualifies. In addition, it can't favor officers or highly compensated employees. Specifically,
Educational assistance program.
An educational assistance program is a separate written plan that provides educational assistance only to your employees. The program qualifies only if all of the following tests are met.
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The program benefits employees who qualify under rules set up by you that don't favor highly compensated employees. To determine whether your program meets this test, don't consider employees excluded from your program who are covered by a collective bargaining agreement if there is evidence that educational assistance was a subject of good-faith bargaining.
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The program doesn't provide more than 5% of its benefits during the year for shareholders or owners (or their spouses or dependents). A shareholder or owner is someone who owns (on any day of the year) more than 5% of the stock or of the capital or profits interest of your business.
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The program doesn't allow employees to choose to receive cash or other benefits that must be included in gross income instead of educational assistance.
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You give reasonable notice of the program to eligible employees.
The exclusion amount is up to $5250.
So if there is one owner (100% shareholder) they would have to pay out at least $105,000 in tuition and loan assistance to other employees in order to qualify for their own exclusion of $5250.
