How to check if the right students have been selected the in course settings

Hover the mouse over the tile of the course and open the course settings How to change course settings?

Click on the Students/Groups field.

a) If all students from the class attend this course, it is right to click the first option "Select all students from selected classes".

b) In case this is divided class course (only part of the class attend your course), click "Select students attending this course"
and tick only the students that attend your course.

c) In case students from several classes attend your course, click the "Selected classes" field, then tick "The course has students from multiple classes" checkbox and select the relevant classes.

If only some students from these classes attend the course, click the "Select students attending this course" option and mark only students you teach.