To provide a student with an extension on an assignment in Microsoft Classroom, the following steps would need to be taken:

1. Open class in Microsoft Classroom
2. Choose the assignment that needs to be extended
3. Tap/click on the assignment set
4. Select the student or students that need an extension
5. Tap/click Update to set the new due date
6. Take note of the modified due date as well as the currently due date
7. Send all students involved an alert letting them know of the changed due date
8. Save changes as needed