Adding more stories to keep the developers busy

Hi, my name is Joshua and I work as a Scrum Master for a small IT company. I was appointed in place of the SM who left a month ago, and after joining I observed that the team had a habit of adding more stories in the sprint than it can handle. The idea is to ensure that developer don't run out of work and should remain busy. The team consists of 2 senior developers and 3 junior developers. The company has transitioned to Agile approximately 6 months ago. After joining, I immediately put a stop to this habit of adding on more stories before the older ones are completed. This has, of course, created many debates, and the CTO is now intervening by allotting stories and tasks directly to the team. I understand developers should remain busy with work and should not remain unoccupied, but due to this type of Scrum implementation high-ranking stories are not being developed so the value of the project is not maintained. The CTO argues that all stories will be completed during the sprints so there is no need to prioritise them - all of the stories are important for the project. I need suggestions how to go about this issue. Cheers!

Posted By - ross