I am the opposite of "glad" about this. It's highly concerning to me. My sister is also a school teacher and her students are just 4th graders and see this as legitimate life goals. Think of how that forms the development of a young child.
It depends.
Option 1:
"Hey buddy. So you want to be a youtube star. Which ones you like? The funny ones? The lifters? The fashion vloggers? It's actually a lot of work. You will need a script, a cameraman, a director, actors etc. And all said and done, for every youtube star, there are tens of thousands who just toil in obscurity. But that's a risk which comes with a lot of life's decisions and you can decide later on if you really want to do it or if you want to do it part time.
Back to the production process. It's not very different from what we do in our school's theater except that there is a massive potential increase in your reach. Why don't you try coming up with a concept and I can walk you through the iterations it takes for the final product. We can even try to schedule a screening for the class and put it on youtube."
Option 2:
"Youtube star? SMH. What has become of today's generation?"
Well at least it is a goal.
When I was in secondary school in the UK ( mid-1980s ) career guidance was just being introduced as a concept. I think it was a couple of half-hour sessions one year and then being left with a folder of job descriptions.
So most of us in my year left school and picked a university course without having any career goal or aspiration. I am mid-40s now and still don't know what I want to do but unfortunately it is too late for many opportunities.
I have a good friend who was the school sports champion and even she just fell into an unrelated career by accident.
If kids today want to be YouTube stars then that's great, hopefully it will give them an objective and a reason to study particular subjects instead of "the teacher seems nice" or "I need to pick one subject from that category"