Originally Posted by
colossus
^^ Actually, the reason why it will be done randomly is for the people not to be prepared not to take drugs in days prior to the test. If they know when they will be tested, they could simply not take drugs in a matter of days and they won't be detected. Hence, the random testing so that it will really be a test to everyone.
Since they could not foresee when the test would be done and to whom, the students must not really be into drugs. It will be more beneficial this way.
And that should be the case for everyone too (college and professionals) as what I have thought. Kung high school lang, that spares the tertiary level and work force which I believe has a significant number of drug users.