Hi,
Indeed, the attachserial plugin can only use the exact data stored in the custom field ( so 0 or 1 in this case ).
The only way I can see to display something else than 0 or 1 would be to develop a small plugin for HikaSerial, implementing the events onGetCustomAttachSerialFormats(&$new_types, &$new_formats) and onCustomAttachSerialFormat($format, $format_ex, $content, &$img, &$d)
In onGetCustomAttachSerialFormats, you want to have such code:
$new_formats[] = JHTML::_('select.option', 'studentdiscount', 'Student Discount');
In onCustomAttachSerialFormat, you want to have such code:
if($format!='studentdiscount') return;
if(!empty($content) && $content > 0)
$d['text'] = 'Remise étudiante';
That will display "Remise étudiante" on the image generated by the attach serial plugin if the value of the field is 1 and will not display anything on it if the value is 0.
You'll have to select the type "Student Discount" when configuring the attach serial plugin in Hikaserial.
If you're a developer, it will be trivial to create the plugin and add the code above in it. If not, it's something we could do for you for a small fee.