Akmol Hussein, 26, Sheikh Rashid, 27, Azad Hussain, 25, and Simon Alam, 19, attacked Gary Smith with a Stanley knife, an iron rod and a block of cement.
Mr Smith, who is head of religious education at Central Foundation Girls' School in Bow, east London, also suffered a fractured skull.
The four now face a jail sentence.
Detectives made secret recordings of the gang's plot to attack Mr Smith prior to the brutal assault.
The covert audio probe captured the gang condemning Mr Smith for 'teaching other religions to our sisters', the court heard.
The RE teacher was targeted as he made his way on foot along Burdett Road in nearby Mile End on July 12 last year, Snaresbrook Crown Court was told.
Prosecutor Sarah Whitehouse told the court: 'The evidence from what was said on the probe points overwhelmingly to a religious motive for this attack.'
It is believed the gang had made two earlier attempts to get at the teacher.
They were due to stand trial for the attack at Snaresbrook Crown Court but pleaded guilty to causing grievous bodily harm with intent.
A fifth defendant, Badruzzuha Uddin, 23, admitted assisting the thugs by hiding blood-stained clothing.
Judge John Hand QC remanded the defendants in custody until sentence on a date yet to be confirmed.
Hussein, of Bethnal Green, east London; Rashid, of Shadwell, east London; Hussain, of Wapping, east London, and Alam, of Whitechapel, east London; have all admitted causing grievous bodily harm with intent.
Uddin, of Shadwell, admitted assisting an offender.
These unprovoked pack attacks on lone infidels have reached epidemic proportions and are known as 'Street Jihad'