I don't have to.

I live in one of those areas that it is possible that at least 30% of kids in a class is at least mildly gifted. I also work with people with Ph.D in fields that is highly quantitative. So I assume most of my friends' kids are at least MG until proven otherwise.

Now, PG or EG is another matter. Those are still rare. But they all have parents who are super aware, I have yet to run into a case that I feel the need to point it out.