What leftists can prove is that every Republican President since Reagan has crashed the US economy, enriching the wealthy, and improverishing the working and middle class - all while blaming "leftist policies" and social spending.
And yes, we can prove the DEI is more profitable, more intelligent, and more creative than straight white men. That companies do BETTER when their workforce reflects their communities. That MERIT rather than sex or melatonin should determine who is hired, and merit includes the ability to work within a diverse community.
And yes we can prove that a public education system which isn't being manipulated by right wing radicals and those who ban books and deny climate change, produce a much higher level of education and quality employees than the US education system, which is taking money out of public education system and giving American parents "choice". Far too many are chosing racist, misogynistic, anti-democratic church schools, and/or home schooling to allow parents to indoctrinate their children into all manner of idiocy.
Your test scores are falling, and you poor are poorly educated at best. You're one of two first world countries who spend more money educating the children of the rich than you do on the children of the poor. Turkey is the other.
Your whole model is starving inner city schools of resources, to keep a poor, uneducated underclass dependent on government handouts to survive, to serve the upper and middle classes. Wage slaves. Really poorly paid wage slaves.
They're a Republican red-state creation.