advisor - Is it appropriate for assistant professors to supervise PhD students?

As pointed out in another question, the general tendency today as compared from classical times is to make junior professors (at assistant level) more and more independent. However, I wonder that assistant professors (common in the US university) supervise PhD students.

The philosophy of academic ranking is to prepare academics for academic/scientific tasks.

Although, academics normally have postdoc experience before their appointment as assistant professors, it is not mandatory. Moreover, postdoc experience is not experience conducive for the supervising of students.

In relation to the above is it wrong that an inexperienced assistant professor (who is not far from his PhD studentship days) can take control of one or several PhD students?

Does it reduce the quality of the education/research?

Answer

Isn't it wrong that an inexperienced assistant professor (who is not far from his PhD studentship days) can take control of one or several PhD students? Don't it reduce the education/research quality?

For certain institutes I've been in, I would find myself asking the opposite question: isn't it wrong for senior professors to supervise students when they have little time for them?

Of course it is not always the case that full professors have no time for their students, but I have seen it happen many times: I've seen cases where students were meeting their official full professor supervisors once a month (or less frequently) and putting names of supervisors on papers that the supervisors had never read. This seems to me to be prevalent in research institutes where the hierarchy tree has a high branching factor to get value out of available funds (few Full Professors, lots of PostDocs / Assistant Professors, even more PhD students and Research Assistants, etc.); in such cases, the priority for senior professors is getting funding for and managing projects. In my case, when I was a PostDoc in such an institute, I was doing the day-to-day supervision of a number of students whose supervisor(s) had no time for them.

Of course it varies from place to place. But my hypothesis is that by the time you reach the Assistant Professor level, either you will have the necessary skills and personality to be a good supervisor, or you will probably never have those skills.

In summary: I don't believe that seniority amongst professors is a good predictor for quality of supervision.