Mr Hassett, of Dolphinholme Church of England primary, Lancaster, will teach every morning and two afternoons a week - an increase of 10 per cent.
"My staff will try to help me because we are a good team. But I would never take PPA time from them. I wish I had had it when I started out. They already do more than their fair share. Besides, I am not prepared to break the law.
"My governors are not happy and neither are my staff. They are worried about my health."
Mr Hassett has reserves of pound;4,600 to pay for the scheme. After that the funds dry up: "You tell me what is going to happen next year. I haven't thought that far ahead because I daren't.
"I do not have enough money to do anything but take on more teaching. Most heads in small schools are in the same situation. We can't get football coaches in during PPA time. They will only go to big schools where they can stay the day and earn more. We would only need them for an hour.
Mr Hassett already spends one day out of his weekend planning and preparing lessons but he is determined to spend the rest of his time with his two daughters, aged nine and 11. "Something has got to give and it is not going to be my family.
"I will run the school as effectively as I can and I will make sure standards do not slip but things are not going to get done as quickly," he said.