Symfony2/Doctrine: How to re-save an entity with a OneToMany as a cascading new row

Firstly, this question is similar to How to re-save the entity as another row in Doctrine 2

The difference is that I'm trying to save the data within an entity that has a OneToMany relationship. I'd like to re-save the entity as a new row in the parent entity (on the "one" side) and then as new rows in each subsequent child (on the "many" side).

I've used a pretty simple example of a Classroom having many Pupils to keep it simple.

So me might have ClassroomA with id=1 and it has 5 pupils (ids 1 through 5). I'd like to know how I could, within Doctrine2, take that Entity and re-save it to the database (after potential data changes) all with new IDs throughout and the original rows being untouched during the persist/flush.

Lets first define our Doctrine Entities.

The Classroom Entity:

namespace Acme\TestBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\ArrayCollection;

/**
 * @ORM\Entity
 * @ORM\Table(name="classroom")
 */
class Classroom
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=255)
     */
    private $miscVars;  

   /**
     * @ORM\OneToMany(targetEntity="Pupil", mappedBy="classroom")
     */
    protected $pupils;

    public function __construct()
    {
        $this->pupils = new ArrayCollection();
    }       
    // ========== GENERATED GETTER/SETTER FUNCTIONS BELOW ============

}

The Pupil Entity:

namespace Acme\TestBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\ArrayCollection;

/**
 * @ORM\Entity
 * @ORM\Table(name="pupil")
 */
class Pupil
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")