Officers were called to Thorpe St Andrew School, Laundry Lane, Thorpe St Andrew, at 10.24am on Wednesday following reports a girl had been stabbed.
A 16-year-old boy has been arrested on suspicion of causing grievous bodily harm with intent, Norfolk Police said.
The boy has been taken to Wymondham police investigation centre for questioning, the force added.
The victim has been taken to hospital with minor injuries.
Emergency services including fire and ambulance crews were at the scene.
Armed police officers were also at the school, reported the Eastern Daily Press.
The school was described as being in lockdown conditions with pupils hiding beneath their desks and some having their phones confiscated, the newspaper added.
Norwich North MP Alice Macdonald wrote on social media: "Reports from Thorpe St Andrew School are incredibly serious and deeply alarming.
"Immediately, we need to give the police time to ensure that everyone at the school is safe.
"My thoughts are with all of them and their families, especially the victim who has been taken to hospital."
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The school, which was rated "Good" in its 2025 Ofsted inspection, is an 11 to 18 mixed secondary school which also includes a sixth form.
The incident is not believed to be linked to a hate crime reported at the same school last week, police added.
It followed reports of allegations of antisemitic chanting during a football match involving a Jewish school.
They ran into difficulty while swimming at Shellharbour Beach, about 70 miles (114km) south of Sydney, shortly after 11am (local time) on Wednesday.
The 66-year-old man and 64-year-old woman were pulled from the water by members of the public, who performed CPR, before paramedics arrived.
Despite their efforts, the pair could not be revived and died at the scene, NSW Police said.
The couple had been visiting family in the Illawarra region.
Inspector Luke Geradts said some of the couple's relatives were with them at the beach.
"This is a timely reminder of the dangers and unpredictability of the ocean," he said.
"This is a tragic incident, and our hearts go out to the family who lost their loved ones today."
Inspector Geradts praised the actions of two off-duty nurses and a young man who ran to the couple's rescue, recovering them from the water and giving them the "best chance of survival".
"Although a tragic outcome today, their efforts are to be commended," he said.
He said the conditions in the surf had been "rough" and police believe the couple were caught in a rip current.
"We really want to encourage people to swim between the flags… because if you do get into trouble it's going to give yourself the best chance," he said.
"Every time we go to one of these incidents, a family has lost a loved one, and that's what's so hard about it, for a family to lose a loved one," he added.
A report on the couple's death will be prepared for the coroner.
A spokesperson for the UK Foreign Office said: "We are supporting the family of two British nationals who have died in New South Wales and are in contact with local authorities."
Deaths from drowning have occurred across Australia's coastline over the summer, with 50 recorded in coastal waters between 1 December and 2 March, according to Surf Life Saving Australia.
Forecasters have said there could be gusts of 65-70mph, with a small chance of gusts of 75-80mph in a few locations, with rain and blustery showers accompanying the strongest winds.
The yellow warning for wind is in place for northern England, the Midlands, north Wales and parts of Scotland from 5am on Thursday until 8pm.
There is also a warning in place for Northern Ireland from 6am to 12pm on Thursday, where gusts could reach 50-60mph for a short period, along with heavy rain.
Find out the forecast for your area
The Met Office said: "A period of strong winds, accompanied by heavy rain, is expected on Thursday with some transport disruption possible."
A yellow warning for wind is already in place for parts of northern Scotland.
It comes before temperatures are expected to drop across the country on Friday - with snow forecast in some areas.
Christopher England, Sky News meteorologist, said that "it's looking quite unsettled over the coming days, with strong winds bringing gales to northern and western hills at times, locally severe".
He added that "heavy, sometimes thundery, showers or longer spells of rain" are also expected, "although the south-east will be mainly dry until tomorrow evening".
"It'll turn colder too, with snow over northern hills descending to quite low levels on occasion, and some icy stretches."
Joanna Robinson, Sky News's weather producer, said on Tuesday that temperatures are expected to be "widely below average on Friday and Saturday before recovering slightly".
"Friday will bring showers, with snow down to relatively low levels in the north, especially early on," she added.
"There'll be fewer showers around on Saturday, and the snow risk will become increasingly confined to the highest hills."
It also comes after provisional figures from the Met Office at the start of March showed this winter was the wettest on record for parts of the UK.
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Three named storms in January - Goretti, Ingrid and Chandra - all brought downpours to many areas, leading to flooding and widespread travel disruption.
The public will be given the chance to choose which aspects of nature will appear on the notes to "showcase the UK's rich and varied wildlife".
It marks a shift from more than 50 years of showcasing historical people, including Alan Turing and Jane Austen.
King Charles' portrait will continue to appear on the next series of notes, the Bank said.
The change to wildlife imagery will create an opportunity to celebrate another important aspect of the nation, it added.
It will also make it more difficult for the notes to be counterfeited, while making security features more distinguishable.
The move follows a consultation last summer in which the UK wildlife theme received the highest proportion of nominations, at 60%, from 44,000 responses.
In second place was architecture and landmarks with 56%, while notable historical figures was third with 38%.
A second consultation will run this summer to collect views on the specific wildlife the notes should feature.
The banknotes have displayed monarchs since Queen Elizabeth was first featured in 1960, while Shakespeare was the first historical figure to be chosen in 1970.
The new notes will feature wildlife native to the UK - such as plants, landscapes and animals - but will not include household pets, the Bank said.
The notes will "incorporate the latest anti-counterfeiting technology" and it will be "a few years" before they are issued.
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Representation of the Home Nations - England, Scotland, Wales and Northern Ireland - will also be an "important factor" of the design.
Victoria Cleland, chief cashier at the Bank of England, said: "The key driver for introducing a new banknote series is always to increase counterfeit resilience, but it also provides an opportunity to celebrate different aspects of the UK.
"Nature is a great choice from a banknote authentication perspective and means we can showcase the UK's rich and varied wildlife on the next series of banknotes."
The 56-year-old assumed the top position after Ayatollah Ali Khamenei was killed in the initial strikes on Iran, but has not been seen in public since.
Mojtaba Khamenei had been lightly wounded in the strikes but continued to operate, an Iranian official told Reuters.
The new supreme leader has long been a secretive figure within Iran and has not given any public statement since being appointed by an assembly of Iranian clerics on Sunday.
Mr Khamenei lost his father, mother, wife and other relatives during the Israeli airstrike on 28 February.
Speculation has been mounting about the health of the new supreme leader, with Yousef Pezeshkian, the son of Iran's President Masoud Pezeshkian, referring to reports that he had been injured.
In a post on Telegram, he said: "I heard news about Mr Mojtaba being injured. I asked friends who were in contact. They said, thank God, he is healthy and there is no problem."
A state television anchor also appeared to confirm rumours that Mr Khamenei had been hurt, describing him as a "janbaz" or "wounded veteran" of the Ramadan War, the name Iran has given to the conflict.
'Target for elimination'
Iran's Islamic Revolutionary Guard Corps (IRGC) backed the relative unknown as the new supreme leader, viewing him as a more pliant version of his father, who would support their hardline stance.
It's likely the younger Khamenei has sought to keep a low profile due to the risk of further US-Israeli strikes.
Israeli Defence Minister Israel Katz said last week that any leader appointed by the current Iranian leadership would "be an unequivocal target for elimination".
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Mojtaba Khamenei is the second-oldest son of the late supreme leader, and a hard-line conservative who served in the Habib battalion of the IRGC during the Iran-Iraq War in the 1980s, allowing him to build support within its ranks.
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He has also been linked to the violent suppression of protests in Iran.
Although he studied in the holy city of Qom, he was only a mid-ranking cleric, not a senior ayatollah like his father.
He bears a strong resemblance to his father, and wears the black turban of a sayyed, indicating his family traces its lineage back to the Prophet Mohammad.
By allowing Mr Khamenei to inherit the role, the assembly of experts has, in effect, created a dynasty, a move that defies the tradition of selecting the next supreme leader on credentials alone.
US President Donald Trump had previously branded the selection of Mojtaba Khamenei as supreme leader as "unacceptable".
"We want someone that will bring harmony and peace to Iran," he said.