There are many who have ancestors of European descent in North America and Britain who've known this for thousands of years. Personally, I've never heard any white people pronounce 'street' as 'schreet' but I cannot dispute this either nor will I do this. There are two answers to this concerning the white people who pronounciate certain words as so. 1) Some are deliberately 'mispronouncing' certain words that they know they can pronounce correctly. 2) Some actually have the tongue to pronounce these words as such beyond their control. I won't post the reasons why numbers 1 and 2 is possible (in the case of both, black people are included as well), you'll just have to think about it.

The answer is in the Book of Judges chapter 12.