Recently I contacted a research professor at a major US university about being his student. After some days, I emailed the head of the school asking if research professors are allowed to supervise students, he replied no. Today I received a message from this research professor telling me that I need to send him CV and research statement, but why is that?
Normally in the US graduate admissions is up to a committee of the department, not to an individual professor. You need to be admitted before such conversations with a professor are meaningful. Perhaps the head of school just meant that it isn't in the professor's power to accept you and you need to apply normally.