Issue is, this system prioritizes assessment even more than actual learning. So this would be better for getting 'fair' credentials, but it would lead to people

Issue is, this system prioritizes assessment even more than actual learning. So this would be better for getting 'fair' credentials, but it would lead to people 'teaching to the test' even moreso than right now. The current situation where the teacher is also the assessor allows the teacher to chose what to teach, to react to students, to teach for improving their students. Then at the end, almost as an afterthought, the teacher comes up with an assessment. This serves a bureaucratic purpose, the administration requires it. It also serves a motivational purpose "Study the material or you will fail the test", which helps the teacher to actually get students to learn. This does mean the test isn't really focused on assessing how well the students have learned. But do we need more focus, in studying, on assessing how well someone has learned? I'd argue we need more focus on actually teaching well. Using tests to determine the quality of teaching seems quite fraught. Certainly the adversarial model of an assessment makes things harder. To summarize, I think your solution would fall to Goodhart's law: "When a measure becomes a target, it ceases to be a good measure." Whilst also de-emphasizing the actual goal of teaching.