There has been another confirmed case of coronavirus at JCG.
Channel 103 understands it is the third within the school, though this latest one is not in sixth form.
Their year group has been sent home while direct contacts are identified and traced.
The college remains open on Public Health advice, and siblings in other classes can continue to attend.
"The affected student is isolating at home, along with the rest of their household, and is following the public health guidance. In order to respect the privacy of the individual no further information will be provided about them." - CYPES statement
It is the latest in a number of cases within schools.
A pupil at Hautlieu has tested positive, and Years 12 and 13 at Jersey College for Girls, Victoria College, Beaulieu and De La Salle have been advised to get tested following a 'small number' of cases - believed to be three - in sixth formers at JCG and Vic.
A spokesperson for the government told Channel 103 that Contact Tracing Team had advised testing of fellow Hautlieu sixth formers was not needed. No further explanation has been given.