Translation:We finish school at 3 tomorrow.
The problems reported here go beyond the mere 3 vs 3pm. There are attempts at getting the module to accept "Our School", and other inferences in the answer. I believe it is still very difficult a system to actually detect all correct translation variations. Strictly speaking ,only these terms are present there: "We", "Tomorrow", "3 O'clock", "Out of School". I guess the simplest English compliant concatenation would be: "We [will] finish school at 3 tomorrow"
When I get something like that "wrong", I do report it, to help adding strength to the system, yet I just try to capture the intent of the accepted translation, put it as suggested for now, and move on.
This is the most inflexible module yet -- I suspect a different editor worked on it. "Tomorrow at 3 we finish school" should reasonably be considered a correct answer. Such incidences were heretofore rare enough to overlook, but I am now thinking about trying another tutorial. Or perhaps I should say, "I am thinking about trying a another tutorial now." ;)