The actions of a boy who flicked cheese at a teenage pupil, triggering a fatal allergic reaction, were "childish and thoughtless" but not calculated to cause serious harm, a coroner said.
Karanbir Cheema, 13, died after having a severe reaction at his school in west London on 28 June 2017.
A specialist doctor previously told an inquest the death was "unprecedented".
Coroner Mary Hassell said the boy who flicked cheese taken from a friend's baguette was "simply not thinking".
But recording a narrative conclusion at St Pancras Coroner's Court, she said there was a "missed opportunity" at William Perkin School in Greenford to inform pupils of the severity of his "grave allergies".
Asthmatic Karanbir, who had allergies to wheat, gluten, egg, milk and tree nuts, was immediately treated at the school when the cheese landed on his neck.
His condition quickly worsened and he began scratching vigorously at his skin, the inquest heard.
"He pulled his shirt off, screamed and flung himself around the room in panic. He could not breathe," the coroner said.
Karanbir was taken to hospital in a life-threatening condition and died almost two weeks later at Great Ormond Street of post-cardiac arrest syndrome.
Ms Hassell called the school's healthcare provision for Karanbir "inadequate" and said a contributing factor in his death was the fact his allergy action plan was not included in the school's care plan or medical box.
After a delay, Karanbir was administered with an EpiPen, which contained adrenaline that was a year out of date, at the school.
It was not possible to say whether having adrenaline that was in date would have changed the outcome, Ms Hassell said.
She said she now would prepare a report intended to prevent future deaths, which would be sent to Karan's school, emergency services, government departments and experts.
Speaking after the inquest, Karanbir's mother Rina Cheema said: "I think it would help a lot of children out there, whatever happened to my son, if the schools, the institutions, hospital, paramedics, were to become aware how serious allergies are.
"My son was mature, he knew himself how fast to react. His words were at school: 'Please help me or I'm going to die'. That says it all."
Dame Alice Hudson, executive head teacher of the Twyford Trust which encompasses William Perkin School, said: "It's my view that there was a very good general awareness of his allergies in relation to both bread and cheese."