The Department of Education says the Island's secondary schools sell around 7,000 plastic bottles of water in an average week.
A Freedom of Information request asked for details about single-use plastics and bottled water sold in schools.
In its response, the department said only Ramsey Grammar School sells no bottled water - because it sells cartons instead.
And it added St Ninian's and Ballakermeen High Schools made around £94,000 from sales last year, but QEII and Castle Rushen High Schools couldn't provide the sales figures.
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