In one of my college writing classes, my professor was so astonished by the poor writing abilities of my classmates that he had us do grammar worksheets in class together. He would go down each row of students and ask them to say their answers to the class, and 90% of them gave the incorrect answer. It's amazing to me that college students believed that the plural of "woman" is "womans". Oh, and I happened to take classes with adults who were working to be teachers of the children of America. Comforting, isn't it?
And yet my grammar isn't always perfect, either. If you see a mistake in my writing, please comment and let me know. This will not offend me one bit, but will actually make me feel relieved.