There’s a thread in the Parent’s Forum regarding purchasing a laptop which you may find useful if you haven’t already looked at it. Some people make a good observation that purchasing the laptop from the School’s bookstore may include free service by the school’s IT department.
I doubt you’ll run into compatibility issues with a Mac given the prevalence of web-based applications and platform independent file formats (such as .pdf). Apple has also historically had a strong presence in universities. If you’re using Pages, Numbers, or Keynote, you may run into formatting issues when trying to share files with other students using Office. If you decide to go with a Mac, I’d recommend sticking with Office 365. You also have the option of using Parallels or VMWare to install a Windows virtual machine on your Mac just in case you come across some odd situation where a PC is required.