Actually, the test is administered by the public education system and the dictionary is a volunteer job. I see no ethical issues with what they did, the ethics issues lie with the ones that tried to cheat.
I merely pointed out that they are volunteers in order to underline that there is no connection between the state educational system and the private team of volunteers which provide the dictionary service.
So it would only be unethical if they were being paid? I'm not sure what the distinction is.