Max drowned on Sunday on the trip organised by Fleetwood high school, where his 37-year-old mother Patricia works as an educational support assistant.
Although not a pupil at the school, he had accompanied his mother, who was one of three adults supervising the 15 children. Mrs Palmer required hospital treatment after diving into a river near Glenridding to try and save her son. The Health and Safety Executive and Cumbria police are investigating the tragedy.
The Department for Education and Skills is to issue guidelines on trips by the end of July. A handbook will also be published.
Margaret Dudley, the school's head, said Fleetwood could not be held responsible for Max's safety. "He was not a pupil here and the decision for him to attend the trip was taken by his mother. We can't act as legal parent to a pupil whose parent is accompanying him or her."
Max was one of three primary pupils on the weekend, and Mrs Dudley dismissed the notion he was too young to attend.
An HSE spokeswoman said legal liability for Max's safety lay with Lancashire County Council. "He was not a pupil at the school, but he was a pupil of a school run by that authority. However, it is for the courts to decide where ultimate responsibility lies."
A government spokesman confirmed that the employing LEA is usually responsible. A spokesman for Lancashire said: "We need to consider all the facts. But we understand that Max was there with his parent."
Margaret Morrissey, from the National Confederation of Parent Teacher Associations, sits on the Royal Society for the Prevention of Accidents'
safety education committee. She wants schools to examine weather reports up to two weeks before any trip and national safety criteria.
Max attended Shakespeare primary, in Fleetwood, where he was described as a "joy to teach". An inquest into his death was opened on Monday.
The Health and Safety Executive launched another inquiry this week after a 13-year-old girl was injured after falling 15ft while crossing a ravine on a night-time school expedition. Chloe Patel, of Kings Langley secondary, Hertfordshire, was treated for a fractured vertebra after the fall at Llaneglwys, Powys, mid Wales.
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