Not necessarily but it's usually the first part of the course and there is supposed to be (I am not convinced) a correlation between ground & flying pass/failure rates.
The flying is going to test other aspects such as co-ordination in handling & instrument flying skills & later on CRM. There are some who sail through ground school but just can't fly the aircraft to the required standards in the time allocated, this now starts to become expensive. Some even eventually realise they just don't like flying & it's not for them, one reason you should have at least one trial lesson before committing to an integrated course.