Correct interpretation of genitive plural noun when preceded by another plural noun

Question

Which is the correct translation of учитель увидел по глазам учеников, что что-то случилось?

1. The teacher saw in the eyes of the student, that something had happened.

2. The teacher saw in the eyes of the students, that something had happened.

I understand that учеников is in the genitive plural, but I'm confused whether it's plural due to more than one eye (глазам) or because there is more than one student.

Answer 1

As @Dmitry said, the second option is correct. If you translate first expression to russian it will be учитель увидел по глазам ученика, что что-то случилось. And it has nothing to do with eyes, i think in english it would sound as awkward as in russian if you say something like 'The teacher saw in the eye of the students, that something had happened' :D