Once a new student is added to a class in which an assessment is already assigned (i.e. in "Not open" or "In progress" status), then he/she is automatically added to the assignment and teachers can also observe the increase in the count of assigned students. To make it easier, please follow the steps below.
We have a class with two(2) students enrolled, Billy and Bryan (see below).
Once we assign an assessment to this class, the assignment screen of the teacher looks as such:
Note that it also shows the number of students that the assessment has been assigned to.
Next, a new student is added when there is already an assessment assigned in the same class.
Once you have added the student, William, he will be automatically added to existing assignments which are still open for submission. Also, the assignment screen will now show the updated count.
Note: While adding a new student to a class, if the assignments are in "Awaiting Grades" Or "Graded" status then the student is not added to those assignments. They only become a part of the class.