It varies by the type of credit or deduction. For married filing jointly filers, the American Opportunity Credit for undergraduates starts phasing out at $160,000 and is not available at $180,000. The Lifetime Learning Credit starts phasing out at $108,000 and is not available at $128,000. The tuition and fees deduction is not available at $160,000.
The amounts for other filing statuses (except Married Filing Separately where it is not allowed at all) is 1/2 of the married filing jointly limits.