Public school teachers have taken a big step — a fateful one, some would say — by authorizing a new program of random drug testing in the ratification of their union contract.

The real work of putting the program into effect is just beginning, however. Both sides have some important realities to consider before the testing can begin more than a year from now.

The acceptance of the contract was clearly a tough decision for the Hawai'i State Teachers Association rank and file. But it's one that ultimately will restore some public confidence in the safety of the campus environment, confidence that had been shaken by a handful of teacher arrests on drug charges in recent months.

Granted, those scattered episodes should not impugn the reputation of the state's 13,500 public school teachers: These are educators who take up the profession largely out of their concern for the future of our children.

It's the public interest in the welfare of those children that justifies this initiative: The state should commit to ensuring classroom environments are drug-free.

Other public-employee unions, the United Public Workers and the Hawaii Government Employees Association, have advanced further along this path. Their safeguards are worth studying to see how they might apply to HSTA, but it will take detailed negotiations — talks involving broad representation of teachers statewide — to create a final plan that will stick.

Among the issues to be hammered out: