You can reassign the same task to students by using the Duplicate Task function:
This can be found by firstly accessing the task (click on the task from the Planner page). From there, you will be redirected to the 'Create Task' page where you can customise the task, and who to assign the task to:
Then hit 'Save' to assign this task.
Note: Even though you have duplicated the task here, you will see a new set of results for this task.