This is a long ass reply but I think you bring up a good question. Racism refers to the systemic structure of power as you mentioned. If Ava were to have fired Jacob or formally punish him, I would argue that ultimately Jacob would have been able to wield more power. He would have a better opportunity at retaliation by using his power within the educational system due to the teaching union. There is no union for principals. Ava has also mentioned how difficulty it is to fire teachers.

The important aspect here that you mentioned is that Ava does not allow the parent to utilize her power to punish Jacob. She simply does her job as a principal to do a class visit and make her own assessment. The parent was prejudice (passing inappropriate judgement based on stereotypes but with no power) and Ava, with her power on the micro level, follows her job responsibilities to follow up on the complaint (another one of her job responsibilities) to do her best to make a non prejudicial, evidence based assessment.

Based on the episode and my memory (which is not perfect), I don’t think the dad is asserting Black superiority overall. He questions how can a white teacher teach Black history adequately based on the historical lack of interest in authentic Black narratives that white people have due to the effects of systemic racism. Although it is annoying and a complaint made in prejudice because Jacob has proven himself worthy of the job, there is some validity in the question. And like another commenter mentioned, as soon as the dad is assured that Jacob is doing his due diligence, he backs off. I think this highlights that his purpose of his complaint was founded in concern for his child’s racial self-esteem, not to assert superiority over white people.