"Él es popular entre los alumnos."
Translation:He is popular among the students.
In English, to me, being popular WITH the students imples that the popular one could be a student or more probably some other class of person. Being popular AMONG the students would more likely imply that the popular one is a student himself/herself. That's how I would use use the words.
In Spanish, I don't know if such as distinction would be made betwee ENTRE and CON.