I've got decent insight into several local school districts. From less-close information I've picked up from around the country, our city doesn't seem to be an outlier.
For both fully-remote and alternating-day in-person, if schools still failed kids, they'd have had to fail over half of most classes. Percentages of engaged-enough-to-be-OK kids in online schools tended to sit in the 10-20% range. It wasn't unusual for half or more of kids to effectively be absent for an entire semester. [EDIT] The alternating-day half-in-half-out in-person schedule kids, in the one district that I have insight into that did that for fall 2020/spring 2021, seemed to fare even worse than the online cohort, incidentally.
> I’d like to see trends in standardized tests during this period as I think the real harm was in knowledge not gained.
Any places that did them, they'll be awful, guaranteed. IIRC at least some states skipped them in Spring 2020 since it'd have been nearly impossible to proctor them and everyone knew they'd be "tainted" anyway. The main point of them is to compare year-over-year progress to see what needs to be adjusted and whether progress is being made, for which a during-remote-learning standardized test would be worthless, since you already know it'll be bad and why it's bad and won't be able to get any actionable info out of comparing it to prior or future years. It'll probably be another couple years before we have something like a new baseline and the tests start to be useful for their intended purpose again.