"We're not proposing to exempt anything else. Other governments in the future might choose to," Hipkins said.
National's education spokeswoman Nikki Kaye said it was a "very wide power" for the Minister of the day to be able to decide what donations can be asked for.
"The ideal situation would be for the select committee to scrutinise the amendment."
Hipkins said he had informed the select committee of the change, and there had already a lot of feedback from schools about the bill.
"Even if the select committee made the change, they [schools] wouldn't be able to give feedback. Select committees don't double consult. They don't consult on the bill, make amendments, and then consult on the bill again."
He said school camps would be exempt if they were part of the delivery of the curriculum.
"Schools shouldn't be charging a fee, but can ask for a donation for that. Outside of school hours, like a school ski trip, something that's purely optional, schools can charge a fee for that and that's not going to change.
"Things like field trips, swimming, schools actually get operations grants that are supposed to cover those things. We don't expect parents to have to pay for those things."
Primary teachers' and principals' union NZEI told the select committee last month that most schools would be worse off if they accept the Government's offer.
Rosehill College principal Sue Blakely said the school would have to shrink curriculum programmes if it took up the Government's offer.
"It is a great shame that an initiative intended to improve accessibility to rich curriculum experiences for all students in decile 1 to 7 schools is likely to have the very opposite effect," she said in her submission to the select committee.
Rosehill's head of physical education Merrick Rennell, in a letter to the Prime Minister, said the policy would "massively hurt" outdoor education in schools.
"This fees structure proposed will see many, if not all, of our authentic outdoor education programmes disappear from the curriculum, which would be an absolute shame."