I've just released our first lesson sharing capability in Scholaric.
You will notice a new Sharing tab in the lesson dialog. Lessons can be shared upon creation, with any number of siblings. When editing an existing lesson, you can share it with additional students, or unshare it from currently shared students. Sharing a lesson creates a new shared lesson, while unsharing a lesson deletes a shared lesson.
Shared lessons have a common description - edit it in one and it is edited for all those who share it. If you try to edit a shared lesson description, you will be warned, and given an opportunity to unlink that lesson from its shared peers.
To support customization of shared lessons, you can also annotate a lesson, so it shows up only for them. Annotations are not shared between students.
Other lesson information - scheduling, time, and score expression - are copied at the time of sharing, but are otherwise unlinked.
You may also combine lesson sharing with creation of repeating lessons, to create a whole series of shared lessons.