You can limit which lessons your students have access to in a given course by assigning a group of lessons. This will help keep the class together and ensure that they are focusing on a given skill or area.
Open your class and go to Assignments. You will see a list of all courses assigned to your class along with a short performance overview.
Click Options on the course you'd like to edit.
The course options allow you to adjust several settings including the range of lessons students can work on. This can be achieved by entering the range of lessons under Limit Lesson Progress. Click Update Options to save your changes.
Assigned lessons will appear on the student interface with a solid blue stripe on the bottom of the lesson icon. If students attempt to practice lessons that haven't been assigned, they will be presented with a written notice advising them to work on assigned lessons instead.