Generally, you want to report education expenses exactly how they are shown on the 1098-T. If the school did not elect to report the prepaid tuition, as Box 7 was unchecked, then the taxpayer should report the spring term tuition expenses in 2018.
If the school included the payments on the 2017 1098-T, with Box 7 checked, that would be a different story. The IRS says "Qualified education expenses paid in 2017 for an academic period that begins in the first 3 months of 2018 can be used in figuring an education credit for 2017 (if you meet all the other requirements for claiming education credits)." Click this IRS link below for more information.
https://www.irs.gov/pub/irs-pdf/p970.pdf.
