In April, the school reported its first case of TB, followed by a second report in July. A third case was reported in October.
However, MOH said the three cases were independent of one another.
The Tuberculosis Control Unit screened about 180 teachers and students who had been in close contact with the first two infected students.
Some screened tested positive for the latent form of the disease and were offered an anti-TB drug to reduce their risk of developing the disease.
About 40 who had close contact with the third student will be screened after the GCE 'O' Level Examination in the middle of November.
It is important to distinguish between those who have tested positive for a latent tuberculosis infection and those with an active tuberculosis disease.
Those with a latent infection do not have any symptoms and the infection is not contagious. Only a small percentage of them will develop an active TB disease in their lifetime.
The TB Control Unit said screening those who were in contact with TB cases is better than a mass screening.
Tan Tock Seng Hospital TB Control Unit head Sonny Wang said: "When you apply a test, you have to apply to a high risk-high prevalence of the condition.
"If you apply a test to a low-risk group, in other words, the prevalence of the condition is low, you will throw up more false positives."
MOH also stressed that Singapore residents still form the majority of TB cases, in response to a news report that highlighted foreigners as contributing to TB cases here.
Communicable Diseases Division director Jeffery Cutter said: "The numbers that were quoted and published there included a lot of very short-term visitors, applicants for work passes who are rejected and go home, persons who specifically come to Singapore for TB treatment, so this number should not be included in comparison with the resident population."
The ministry also said Singapore's current TB cases mainly come from older people, who have a weaker immune system.
