@BroDrillard @sickburnbro Goodness...
I wasn't sure the source and I went through and found where I got the info.
It's from literature on child language acquisition that a guy was talking about on a podcast. So the exact source I don't know, but there is extensive academic literature available if that's what you're interested in.

I suspect that they haven't done huge amounts of work in racial diferences in child language acquisition because the obvious fact that most adult blacks speak English worse than a white child... would not be something you'd keep your job if you talked about too much. But I don't really know because google is fucking useless and I've not read enough in that literature to be able to say.

Actually I'd like to know what percentage of blacks actually speak in "ebonics".
And I have a pet theory (with no convincing evidence supporting it) that jews are gifted at picking up languages and that's one of their advantages as rootless cosmopolitans. It may not be true, but there certainly are jews all over linguistics and second language research. I suspect that's an adjunct to their program of mass migration. Getting those migrants to speak the local language can only make replacing white people easier.

Of course openly investigating those questions would not get you tenure.