As you know, there are three aspects you must master to be perfectly bilingual and speak both languages fluently: oral communication, and reading and writing. Some people may have a bit more trouble reaching the CBC level. When we say that a principal has not reached the necessary level, that probably involves only one of those aspects, and it does not mean that he or she is not able to do the work on a daily basis. That said, I can assure you that those who have not reached the necessary level regarding those three aspects are taking language training.
On April 24th, 2018. See this statement in context.