The year 11 pupil at Teign School in Kingsteignton, Devon, was "recovering well" and is a "low infectious risk", said Public Health England (PHE).
It added that TB screening was being offered to pupils who had had close contact with the affected pupil.
PHE said students should attend school as normal.
About 200 children from the school were found to have latent TB, the form of the disease which is not infectious, last year.
PHE said while the year 11 pupil had the "active" form of the disease, there was a "low risk" of any further cases emerging.
Tests would show if the case was connected with last year's outbreak, PHE added.
Dr Sarah Harrison, consultant in health protection for PHE South West, said: "Parents should be aware of the symptoms of TB.
"Should their children show these symptoms, they should seek advice from a doctor. The symptoms to look out for are a persistent cough for more than three weeks, feeling unusually tired or ill."
Head teacher Mark Woodlock said: "It is always difficult to share news that one member of our community is not well.
"We are working closely with Public Health England to ensure that immediate action is taken to locate and treat any individuals who may also be affected and that parents are provisioned with all necessary information."
A pupil is being treated for tuberculosis at a school that had an outbreak last year.