OLAS/app/models/Rubric.php

<?php

class Rubric extends Eloquent
{

    /**
     * Searchable rules.
     *
     * @var array
     */
    protected $searchable = [
        'columns' => [
            'name' => 10,
        ],
    ];

  public function professor()
  {
    return $this->belongsTo('User')->orderBy('created_at');
  }

  public function activities()
  {
    return $this->belongsToMany('Activity', 'new_rubric_activity');
  }

  public function getCriterion($id, $criterion_id)
  {
    $rubric = Rubric::findOrFail($id);

    $rubric_contents = json_decode($rubric->contents);

    foreach ($rubric_contents as $key => $criterion)
    {
      if($criterion->id == $criterion_id)
      {
        return $criterion;
      }
    }
  }

}