A court has heard that a care home had "systemic failures" before a 16-year-old drowned at a former quarry.
Umar Balogun, who was being cared for at Castle Lodge home, Cambridgeshire, died while swimming at Bawsey Pits, Norfolk, in July 2013.
The Old Bailey heard that Castle Homes Limited failed to carry out proper risk assessments and had admitted breaching health and safety rules.
Two support workers who faced charges over the death were cleared in January.
At a sentencing hearing, prosecutor Quentin Hunt said employees of the home had taken boys on a trip to the former quarry.
Umar drowned after going into the water despite "no swimming" signs around the site.
Mr Hunt said: "Mr Balogun was seen to duck under the water and did not reappear.
He added that while there were "generic risk assessments", individual assessments were not made for trips like this and said there was "systemic failure" at Castle Lodge over a "long period".
"The company was directly and immediately responsible for the trip from the home which resulted in the fatal accident."
Judge Mark Dennis QC indicated he would reserve sentencing until after he had considered the case.
Umar was at the lake with another boy and the two care workers, who had not seen a document which said Umar was a "high risk" for swimming, Norfolk Coroner's Court was told in 2015.
Umar's death was accidental, an inquest jury ruled.
Ryan Pettengell, 41, of King's Lynn, Norfolk, had swum out to look for Umar but he got into difficulties and also drowned.