It really depends on the person. I've taught several people how to brew, usually on my system, but the best students are those who watch a brew day before they get into it personally.
My fiance' is a good example for this. He watched me brew a couple times, then decided he wanted to help (e.g. cleaning and the occasional hop addition), then decided he wanted to brew on my rig by himself. He asked me to supervise and give direction when needed, but he handled an all grain brew pretty well with little interaction from me. Fast forward to a couple weeks ago, when he brewed his first extract batch on his very own system, he was like a seasoned pro - knocked it out in 2 hours with no problems. I was there to give helpful tips and tricks, but I mostly just sat and watched.