Yes it can be and is at an individual level.
If you removed 50 points from every Black student's SAT score just because they were Black, there would still be countless other factors that caused them to succeed for fail at getting into college. Their being Black wouldn't be the largest factor (family income still would be).
But across the entire population, you would see a significant drop in the number of Black students in college.
As to a link: Here's a link and a quote from the abstract of a relevant metastudy
https://www.ncbi.nlm.nih.gov/pubmed/26090843
"The results showed a negative and moderate relationship between dialect use and overall literacy performance (M effect size = -0.33) and for dialect and reading (M effect size = -0.32). For spelling and writing, the relationship was negative and small (M effect size = -0.22). Moderator analyses revealed that socioeconomic status and grade level were not significant predictors for relations among dialect use and literacy skills."
From the beginning I've not denied that dialect can have an effect, only that I believe it to overwhelmed by a sea of countless other factors that cause someone to succeed or fail at getting into college, and I haven't seen any data that shows that it is the prevailing factor and one that truly matters.
The subtext to my comments is that this a debatable point, and I interjected because others were throwing veiled insults and calls of racism at anyone who tries to discuss this, which is an unfair way to shut conversation down.