These are entirely my statements & opinions and are not legal advice.
The BBC are quite clear that the micro:bits are the property of the student.
To ensure the micro:bits are available for class work, it is not unreasonable to keep them at school until the end of term.
To prevent the waste of a significant percentage of the micro:bits there are a number of possible strategies:
- Require student effort: In the context of the tone of the BBC letter to parents asking for permission for students to use the BBC website, ask those students that want to take a micro:bit home to get their parents to complete the BBC letter permission slip and confirm that the parent is happy for one to come home. The BBC letter is at https://www.microbit.co.uk/terms-of-use
- Donation: Ask parents to allow the school to keep the micro:bit if their child does not want to continue working with it.
- Buy them for a nominal sum from students – eBay are seeing prices around £30 so this will only work if the students haven’t done any prior research.