What was the topic of their conversation last time?

M: Good morning, Cathy.
F: Good morning, Professor. What is our topic today?
M: Last time, we were talking about the Continental school system, and you have shown great interest. So today, we’ll continue with the same topic and talk about the British educational systems.
F: I know there are many famous public schools and institutions like Eton, oxford and Cambridge. They play an important role in the whole educational system.
M: You’re right. But do you know exactly how many students are there in these famous school or institutions?
F: No, what I know is what everyone knows.
M: Oxford and Cambridge are universities each having about 12,000 students out of a total 250,000 students at all British universities.
F: Wow, that’s quite a large number. What about the public schools? Do they have as many students?
M: You have made a mistake here. Do you think these public schools are public so they must have a large number of students? However, in spite of their names, they are not really public at all, but independent and private secondary schools taking boys from the age of thirteen to eighteen years.