PHP SELECT Query in FOR LOOP not executing - select

Question

I have a SELECT query in the FOR loop that will just not return a value, I have echoed the parameters and also run the SQL and they appear fine.
Any ideas as to where I am going wrong?
I am posting values from a multi row form that has the following text fields:
F1,
Grade_system_id
Grade
Grade_System_id
I want to look up the Grade_Points using Grade and Grade_System_id, but not able to.
The error checks dont suggest any errors.
foreach ($_POST['F1'] as $Lesson_Class_id => $Response) {
$Grade_System_id = $_POST['Grade_System_id'][$Lesson_Class_id];
$G1 = $_POST['G1'][$Lesson_Class_id];
$Lesson_Class_id=trim($_POST['Lesson_Class_id']);
$I1 = $_POST['I1'][$Lesson_Class_id];
$stmt = $conn -> prepare('SELECT Grade_Points FROM Grades WHERE Grade=? AND Grade_System_id=?');
$stmt -> bind_param('si', $G1, $Grade_System_id);
$stmt -> execute();
$stmt -> store_result();
$stmt -> bind_result($Grade_Points);
$stmt -> fetch();
echo $G1;
echo $Grade_System_id;
echo $Response;
echo $Grade_Points;
if ($Response=="Completed") {
$T_Points=$Grade_Points;
}
if ($Response!="Completed") {
$T_Points="";
}
$stmt = $conn -> prepare('UPDATE Lesson_CLass SET I1 = ?, F1=?, T_Points=? WHERE Lesson_Class_id= ?');
//echo 'Student ID: ' . $Lesson_Class_id . ' Outcome: ' . $Response . "<br>";
$stmt -> bind_param('ssss', $I1,$Response, $T_Points, $Lesson_Class_id);
$stmt -> execute();
}
?>
The query is unable to return 'Grade Points'