You can now require that students pass an entrance exam before being able to access your course. Here’s how it’s done:
Start from Studio, and navigate to Advanced Settings (under the Settings drop down menu) 
Scroll down to the section titled “Is Entrance Exam” and type “true”
Click “Save”
For the second step, go into Schedule & Details
Scroll down to the Requirements section and check the box under Entrance Exam
Now, you simply must decide what grade prospective students must earn before being granted access to the course. Then click Save!
Now, if you go back to your Course Outline, Open edX will have already created a section titled Entrance Exam for you to begin authoring.
Important:
After you enable an entrance exam on your course, any student who has not passed the exam will
only be able to see Course Updates and the Entrance Exam (like the image below). So be sure to author your entrance exam before you want to start inviting students! 