So here is the deal.
Using namespace is a convenience. However, in the context of teaching, and learning, it has so many draw backs, I think it’s not worth mentioning.
People are very familiar with lumping things into boxes. Whether it’s politics, their jobs, or even education, there are boxes/patterns, and people are constantly putting things into them.
When you teach people to put using namespace std, they immediately go into pattern recognition mode. They learn, as I did in college, that you simply put that at the top of any main file. This will be good for them in the vast majority of cases, but it is incorrect. When they hit that wall, and they will, they will have a huge wtf moment.
I feel it’s better to explicitly state the namespace, that way you are teaching them that these things are in a specific “box”. Maybe later, down the road, teach them about using. You should teach them the way first, then the conveniences later. You learn how to program a linked list, before learning about including the list library. The same should be true for using. Teach them about the “boxes” first, then teach them the short cut.
Just my two cents. Having said that, I would prefer people be coding in any way, than not at all. So even if you learn using right off the bat, I salute you. Keep at it.