How do business schools teach accounting if the professors don't have enough experience?

Very bookishly. I can say that with full confidence, having taught accounting for 36 years at private as well as public universities/colleges, first as faculty member and then as department chair and director of graduate programs. In the old days there was a presumption that you taught accounting only when you had the competence in the subject matter, and that for accounting also meant meaningful practice experience. Then over a period of time since the Ford Foundation report (popularly known as Gordon-Powell report) universities as well as the accreditation body AACSB have de-emphasized practice. What is more important is that you know how to use statistical packages and are an expert at statistical lingo translated for economics. Now you have boatloads of PhDs with people who have learnt with nothing but books from people who too have learnt everything from people who also have learnt only from books. These days, for a sizeable accounting PhD students, in addition, English too is a second (or third) language also learnt from mostly books taught by people who also learnt it mostly from books.

It is difficult to change the situation when accreditation bodies such as AACSB insists on classifying faculty (AQ and PQ, etc.) the way the immigration inspectors at Ellis island classified prospective immigrants in the good old days. Those days, they were worried about immigrants becoming public charges and were not from the “right” countries. These days in accounting, it is to make sure that the faculty have “published” so called “papers” of almost zero consequence to accounting practice in journals that no practicing accountant dare to read for fear of mental derangement.

I would suggest students ask instructors if they have had practice experience. The problem that accounting academics like me faced was reconciling our need to be respected as scholarly colleagues while at the same time proud of our heritage as teaching a profession to aspiring future practitioners. These days, accounting faculty have consigned the latter to the trash heap while really failing in the former.