When using Classroom Mode, if you are logged into the students section by using the school access code and do not see a student's name among the list of students, the following might be the problem:
1) You have not created a project for the student to submit his/her artwork. You can login to your teacher section and click on the projects button and add new project if there is none listed.
2) The project you created did not allow that student's grade / group to submit entries. You can login to your teacher section and select the project and edit details to make sure that student has access.