If you can't find the error, delete the student and re-enter the info.
Go through the entire education interview until you reach a screen titled "Your Education Expenses Summary". Click delete next to the student's name. You'll then get the "Your Education Expenses Summary" screen again. Click the "Add a student" button.
If that doesn't help, tell us what you are trying to accomplish (claim a tuition credit, report scholarship income, report a 529 distribution etc.)