You can receive up to $5,250 from your employer as tuition assistance to take job related undergraduate courses tax-free.
The tax exemption only applies to undergraduate college courses; grad level courses are not tax deductible. The only requirement is that the classes have to be work related.
However, there is a little loophole that can help people take graduate level courses and still claim $5,250 in tax exemption. You may still be able to take graduate level courses if the tuition assistance that you will receive from your employer is used to further your skills in your trade; it can't be something that prepares you for a new career.
This means simply that if you are a lawyer with a large firm, you can use the tuition assistance program to take law courses to further your law career in your company. The money you receive from your firm for the course is tax-free. But if you start taking hospital administration courses at night using that money, you can't claim the deduction.
So try to stay within the bounds of the tax law and enjoy the tuition assistance benefits to further your education.