Those responsible for slavery in the North American English-speaking colonies weren't either Democrat or Republican, they were wealthy landowners growing labor-intensive crops in the Southern colonies.  Congress banned the import of slaves to the United States in 1808 (though smuggling continued).  The Democratic Party was established in 1828.

The reasons blacks haven't been able to escape the inner cities (a 20th century problem deriving from black-lining during the Great Migration) are social and economic; blacks couldn't buy homes in white neighborhoods, even if they could afford them.  This was not caused by either party, it was the outcome of widespread racism and fear of "neighborhood busting".

Schools are funded by local taxes, and poor neighborhoods can't afford good schools.  This isn't owing to Democrats, this is more often owing to Republican insistence that school revenues be local, rather than pooled; so it is a political policy decision.

Your post is propaganda.