Information obtained under the Official Information Act showed Ms Isaac would be required to work five days a month and the Charter Schools Working Group would meet twice a month.
Ms Isaac would be paid $510 a day and the group's six other members $375 each. The rates were set under the Cabinet Fees Framework in February.
In a letter, Associate Minister of Education John Banks told Ms Isaac the chairwoman would be required to commit to working five days per month, but would commit more time during the initial months. She would be required to dedicate three days per month to the role in 2013 and 2014.
Over the three-year period Ms Isaac would be paid $67,320 for her efforts. Her colleagues would receive $18,000.
Cabinet decided members of the working group would be paid at the second highest level in the fee framework which says the chairperson can be paid $360-$655 and members $270-$415.
Mr Banks said the level of payment was reasonable.
"The payment was well within the guidelines set out for such a position in the Cabinet Manual."
Ms Isaac would also be paid expenses including accommodation, meals and travel to include the cost of running a car.
Ms Isaacs said the rate of pay was fair and she had dedicated more time on deciding on setting up charter schools than she would invoice for.
"I think it's fine, it's not comparable to any commercial job; but that's alright; I am not doing it for the money," she said.
"I've dedicated a lot more than that. I haven't put in an invoice yet, but a lot of the time I won't be charging for," she said.
"It's a lot of time to do the job well, more than I expected. I am working how to reorganise my schedule to give it more time," she said.
John Banks wrote to Catherine Isaac on March 27 to confirm her appointment to the role of chairwoman and outlined what the role would include.
"Your role [as chair] will include providing leadership to the group, and managing any conflicts of interest among members notified to you, or that you become aware of as work progresses," said Mr Banks.
An excerpt from an Education Report in February says any members who are already public servants would not receive a fee if they participated in the working group as part of their paid employment and would be paid only expenses.