Note that one of the problems of deleting a grading standard is that it may still be in use - if it were deleted there would be a problem about what do the existing grading entries now mean? In a recent program, I address this issue by reading the old grading standard ( rescaling by 100x - as the POST and GET values are scaled differently!) and then update it - carefully preserving the previous content - thus there is no change it how previous grades are rendered but allowing new "grades" to be inserted. Because this is such a dangerous operation, I force the user to give a "--force" flag to the program.
See the program add_students_to_examiners_section_in_course.py
The program is at https://github.com/gqmaguirejr/Canvas-tools
More details about this and the workflow are at https://community.canvaslms.com/t5/Idea-Conversations/Clearly-document-the-values-for-GradingSchemeE...