Perhaps the versions commonly broadcast now are from the DVD version. Wikipedia suggests in the DVD version of the show, "the original opening and closing credits have been replaced by a single standardized version, eliminating all guest cast and additional crew member information." (citation needed). --Our Miss Brooks - Home media
For comparison, the end of the Wikipedia article links to some episodes on the Internet Archive. The first three episodes in that list have end credits that include various minor characters. (The last one in that list has its recording end just as the ending "OUR MISS BROOKS STARRING EVE ARDEN" begins to scroll up.)