Охарактеризуйте второй этап энергетического обмена

I go to a pablic school.
Yes, I do, boys and girls study together.
After the lessons I go home.
Every day I have 6 or 7 lessons.
No, I don't. Fortunately, I  do not wear a school uniform.
I am lerning one foreign language. It is English.
My favourite subject is PE lesson.
My school has 4 floors.