Yii not filtering model as expected - issue appears to be form related

I have a form that uses a selgridview to enable an admin to select/deselect rows and update the database table.

This has filtering to enable me to quickly find rows using the ajax search ( $model->ClassroomSearch() ) - for some reason the ajax doesn’t seem to work. I can see the $_GET request in the console but the actual rows expected are not shown.




<?php


$this->widget('ext.selgridview.BootSelGridView',array(

'id' => 'student_select_grid',

'selVar' => 'selected_student_id',

'type' => 'striped bordered condensed',

'dataProvider' => $model->ClassroomSearch(),

'selectableRows' => 1000,

'filter' => $model,

'columns' => array(

    array(

        'id' => 'user_id',

        'class' => 'CCheckBoxColumn',

    ),

    array(

        'name' => 'title',

        'filter' => CHtml::activeTelField($model, 'filter_title'),

    ),

),

));


Yii::app()->clientScript->registerScript('selGridViewLoad_students', "$('#student_select_grid').selGridView('addSelection', [".implode(",",$model->classroom_ids)."]);")



The model is as below:-




    public function ClassroomSearch() {

    $criteria = new CDbCriteria();

    //$this->filter_title = 'Haw'; // if this is uncommented this filters row so this function 100% works


    $criteria->compare('title', $this->filter_title, true);


    return new CActiveDataProvider(OrganisationClassroom::model()->currentUserOrganisation(), array(

        'criteria' => $criteria,

        'pagination' => array(

            'pageSize' => 4,

        )

    ));

}



The model here works perfectly fine - this would suggest the problem is related to my form rather than my model - can anyone suggest what I have done wrong?