The private concert came about due to band member Jules Knight, 26, being the step brother of Dauntsey's sixth former Poppy Salter.
Mr Knight and fellow band members Oliver Baines, Dom Tighe and Stephen Bowman are touring the UK to drum up votes for their nomination in the Classical Brit Awards for Album of the Year.
Mr Baines also has local connections as he is a former pupil of Marlborough College and his family live near Malmesbury.
The quartet shot to fame last November when their self titled album reached number one in the UK Classical Album Chart and top 20 in the UK Pop Album Chart.
The four drove themselves from London, where they are based, to Dauntsey's School in West Lavington for the concert on March 19 in its Memorial Hall.
Beforehand, however, the school's director of music Chris Thompson suggested they sang to the packed dining hall.
The four young men performed to 250 pupils eating their lunch by singing Hallelujah unaccompanied and were given a rousing cheer when they had finished.
After they had lunch Blake performed for 30 minutes in the school's Memorial Hall to more than 300 people, comprising pupils and staff, including kitchen and grounds staff.
They used backing tracks and the audience clapped and waved their arms back and forth.
They sang a spiritual song Steal Away, Hallelujah, the Joe Cocker song Up Where You Belong and the rugby anthem Swing Low.
Afterwards they were inundated with requests for photographs and autographs and then they returned to London to perform at an after show party for TV presenter Alan Titchmarsh.
Mr Thompson said: "Blake were delighted with the positive reaction from the pupils and staff and they described Dauntsey's as the coolest school in the universe'.
"The pupils here are very open minded about music, they experience a wide range of music. They really appreciated the calibre of the singing of Blake."
Source: Wiltshire Gazette & Herald