That's orthogonal to my point. Teacher quality or competence in assessing quality, doesn't have anything to do with whether they assign grades in the ways I've enumerated. I've had absolutely amazing teachers that have graded in those three ways.
Even if they're good judges of quality, it's still a matter of how they determine your grade. Is it good quality relative to what they think your skills are? Is it good quality relative to the rest of the class? Is it good quality relative to what they believe constitutes mastery of the subject? And some teachers curve and some don't.
And I haven't said whether I think teachers should be required to meet standards. I don't even know if it's possible to create good standards.
Even if they're good judges of quality, it's still a matter of how they determine your grade. Is it good quality relative to what they think your skills are? Is it good quality relative to the rest of the class? Is it good quality relative to what they believe constitutes mastery of the subject? And some teachers curve and some don't.
And I haven't said whether I think teachers should be required to meet standards. I don't even know if it's possible to create good standards.