Failed to create assessment result using Frappe REST API

I try to create an assessment result into ERPNext using the REST API.
In ERPNext UI, I just need to fill the student, the assessment plan and the score. All other fields are set using the student and the assessment plan :

I try to do the same thing with the API by sending this message with POST method and URL <root_erpnext>/api/resource/Assessment%20Result


ERPNExt returns this error :
File “/opt/bitnami/apps/erpnext/htdocs/frappe-bench/apps/erpnext/erpnext/education/doctype/assessment_result/”, line 18, in validate
File “/opt/bitnami/apps/erpnext/htdocs/frappe-bench/apps/erpnext/erpnext/education/doctype/assessment_result/”, line 30, in validate_maximum_score
if d.score > d.maximum_score:
TypeError: ‘>’ not supported between instances of ‘str’ and ‘NoneType’

Could you help me to create this assessment ? Thanks.