Probá así y fijate que es lo que estaba mal
Código PHP:
<?php
mysql_select_db($database_connection, $connection);
$query_calificarm = sprintf("SELECT
*
FROM alumnosm where claveasignatura= %s", GetSQLValueString($colname_alumnosm, "text") );
$calificarm = mysql_query($query_calificarm, $connection) or die(mysql_error());
while($row=mysql_fetch_array($calificarm)) {
$to[] = $row['parcial1'];
}
foreach ($to as $valor) {
echo "$valor";
echo '<br />';
}
?>