(This posting includes a handout which you are welcome to use with your colleagues.)
At first, all the teachers wanted to administer the oral test for placing students into one of the four levels of conversation classes. But that enthusiasm waned once they discovered what this commercially-made placement test would entail.
Two major problems with many speaking placement tests (commercial and in-house)
1) The testing process in labor intensive. The scoring rubrics are onerous, ineffective and require time-consuming training.
2) Rather than just focusing on the skills being developed in speaking/conversation classes, the interviewers have to evaluate several peripheral aspects of speaking at the same time.