Present law requires those who want to gain US Citizenship to have been permanent residents for 5 years (3 years if spouse of Citizen) or military service.
Those years are entirely adequate to learn American language, history, geography, civics, math and science (though not in all American public schools—something which also needs changing).
When the previous poster said “Admission to citizenship” I read as “Admission or citizenship,” I think. Sorry, it was late for me. I was thinking that (s)/he was meaning before coming to the U.S.A. that they had to know those things, whoops. You are correct, thanks for responding, I didn’t know the guidelines, time-wise.