Answered Custom Tables - Child Record not being deleted

<!--PUPIL-->
<object class="Pupil" table="pupil" extends="xPDOObject">
	<field key="Id" dbtype="int" precision="11" phptype="integer" null="false" index="pk"  generated="native" />
	<field key="username" dbtype="char" precision="100" phptype="string" null="false" default="" />
	<field key="password" dbtype="char" precision="20" phptype="string" null="false" default="pupil1" />
	<field key="fname" dbtype="varchar" precision="20" phptype="string" null="true" />
	<field key="sname" dbtype="varchar" precision="30" phptype="string" null="true" />
	<field key="Level" dbtype="char" precision="50" phptype="string" null="false" default="pupil" />
	<field key="active" dbtype="int" precision="11" phptype="integer" null="false" default="1" />
	<field key="showgraphs" dbtype="int" precision="11" phptype="integer" null="false" default="0" />
	<field key="user_id" dbtype="int" precision="11" phptype="integer" null="false" default="0" />

	<index alias="PRIMARY" name="PRIMARY" primary="true" unique="true" type="BTREE" >
		<column key="Id" length="" collation="A" null="false" />
	</index>
	<aggregate alias="Myusers" class="Myusers" local="Id" foreign="Id" cardinality="one" owner="foreign" />
	<composite alias="FeelPupilsCharts" class="FeelPupilsCharts" local="Id" foreign="pupcht_pupil_id" cardinality="many" owner="local" />
</object>

<!--FEELPUPILSCHARTS-->
<object class="FeelPupilsCharts" table="feel_pupils_charts" extends="xPDOObject">
	<field key="pupcht_Id" dbtype="int" precision="11" phptype="integer" null="false" index="pk"  generated="native" />
	<field key="pupcht_title" dbtype="varchar" precision="255" phptype="string" null="true" default="Chart Title" />
	<field key="pupcht_act_id" dbtype="int" precision="11" phptype="integer" null="false" default="0" />
	<field key="pupcht_pupil_id" dbtype="int" precision="11" phptype="integer" null="false" default="0" />
	<field key="pupcht_chart_id" dbtype="int" precision="11" phptype="integer" null="false" default="0" />
	<field key="pupcht_user_id" dbtype="int" precision="11" phptype="integer" null="false" default="0" />
	<field key="pupcht_showgraphs" dbtype="int" precision="11" phptype="integer" null="false" default="0" />
	<field key="pupcht_showcomments" dbtype="int" precision="11" phptype="integer" null="false" default="0" />
	<field key="pupcht_img_left" dbtype="varchar" precision="100" phptype="string" null="true" default="0" />
	<field key="pupcht_img_mid" dbtype="varchar" precision="100" phptype="string" null="false" default="0" />
	<field key="pupcht_img_right" dbtype="varchar" precision="100" phptype="string" null="false" default="0" />

	<index alias="PRIMARY" name="PRIMARY" primary="true" unique="true" type="BTREE" >
		<column key="pupcht_Id" length="" collation="A" null="false" />
	</index>
	<aggregate alias="Pupil" class="Pupil" local="pupcht_pupil_id" foreign="Id" cardinality="one" owner="foreign" />
	<aggregate alias="UsersActivities" class="UsersActivities" local="pupcht_act_id" foreign="ua_act_id" cardinality="one" owner="foreign" />
	<aggregate alias="UsersActivities" class="UsersActivities" local="pupcht_user_id" foreign="ua_user_id" cardinality="one" owner="foreign" />
	<composite alias="Feeling" class="Feeling" local="pupcht_Id" foreign="feel_chart_id" cardinality="many" owner="local" />
</object>

var_dump($modx->getPK('FeelPupilsChart'));

$feelPupilsChart->toArray('myprefix.')