It should come as no surprise that a conservative think-tank would immediately blame "K–12 education’s love affair with 'equity'." I don't think I need to read any more of this.
I actually wanted to find a nonpartisan source, but couldn't easily find one that was willing to center the actual central point of the UCSD report: that the university can no longer identify math-ready students due to the removal of standardized testing from the admissions process, and they are begging for UC system to reconsider standardized testing.
If you look at the report, it shows the facts support this claim. UCSD has gone all-in on LCFF+ schools (low income, ELL, foster youth) and the explosion in math and literacy remediation is driven by these admits.
One in three LCFF+ admits end up in remedial math, and the total remedial math population is more than 50% LCFF+ admits.
What was the motivator for this post-2020 change? Equity, or the idea that outcomes for all groups should be equal (regardless of time/energy expended, of course).
As a not-conservative with a child in middle school (in CA) this rings true though. We pulled our son out of a highly rated public school essentially because of this, the whole class was taught to the lowest common denominator.