Directly from Pub. 970
Benefits over $5,250. If your employer pays more than $5,250 for educational benefits for you during the year, you must generally pay tax on the amount over $5,250. Your employer should include in your wages (Form W-2, box 1) the amount that you must include in income.
Working condition fringe benefit. However, if the benefits over $5,250 also qualify as a working condition fringe benefit, your employer does not have to include them in your wages. A working condition fringe benefit is a benefit which, had you paid for it, you could deduct as an employee business expense. For more information on working condition fringe benefits, see Working Condition Benefits in chapter 2 of Publication 15-B, Employer's Tax Guide to Fringe Benefits.
It's commonplace for companies that pay for employees' education expenses that they rely on the employee to remain employed at the company for a certain amount of time. As an employee to benefit from the employer's contribution to the education and leave prior to the agreed period should be held financially accountable.