Full time is different.
Some schools pay a retainer £10-20 per day to cover your costs, then pay you £10-20 per hour.
Others will pay a salary £18,000 - £20,000
I was one of the salaried ones, but have also worked freelance for several schools.
As I said before, you will get out what you put in, but don't expect a fortune and take it out on the students when the wx is c##p! .....many do.