There really is a huge difference in the starting level for different students.
Some people come to their first class and they can already fight - they have good natural instincts, coordination, fighting spirit and possibly some real world experience with scrapping. If a student like this has an open mind for learning they could plausibly learn a basic technique in their first class and actually apply it if they got into a fight the next day.
Other people come to their first class and are completely uncoordinated, have no awareness of their own bodies, and are prone to freezing up under pressure. These students may take weeks or months just to start getting a handle on basic movements and learning how not to shut down when confronted with an attack.
I would guess that in BJJ the average student who trains 2-3 classes per week after 6 months has internalized the fundamentals enough to have a significant advantage over an untrained opponent if a fight goes to the ground. It's harder to say how long it takes for an average student to have reliable skills in the standup portion of a fight, because there is such variance in the degree to which different BJJ instructors actually spend time on standup fighting. Some have it as a regular part of the curriculum, others hardly address it at all. If you are looking at a school where standup fighting and dealing with strikes is part of the core curriculum, then I would say a year of training should get the average student to the level of having some reliable usable skills in all aspects of a fight, with a strong advantage if the fight goes to the ground.
Some people come to their first class and they can already fight - they have good natural instincts, coordination, fighting spirit and possibly some real world experience with scrapping. If a student like this has an open mind for learning they could plausibly learn a basic technique in their first class and actually apply it if they got into a fight the next day.
Other people come to their first class and are completely uncoordinated, have no awareness of their own bodies, and are prone to freezing up under pressure. These students may take weeks or months just to start getting a handle on basic movements and learning how not to shut down when confronted with an attack.
I would guess that in BJJ the average student who trains 2-3 classes per week after 6 months has internalized the fundamentals enough to have a significant advantage over an untrained opponent if a fight goes to the ground. It's harder to say how long it takes for an average student to have reliable skills in the standup portion of a fight, because there is such variance in the degree to which different BJJ instructors actually spend time on standup fighting. Some have it as a regular part of the curriculum, others hardly address it at all. If you are looking at a school where standup fighting and dealing with strikes is part of the core curriculum, then I would say a year of training should get the average student to the level of having some reliable usable skills in all aspects of a fight, with a strong advantage if the fight goes to the ground.