Well folks,
thanks for your views, I think I know how to proceed now.
My reasons are the same as Liz �s.
I dowloaded a Ws sheet recently and stupidly didn �t bother to check it. It was on the present perfect.
Yesterday, I handed it out to my students and then discovered to my horror that it was not only past simple but it was full of spelling errors.
The author has been PMed and was very nice about it.
But to be perfectly honest the biggest mistake was mine for not checking in the first place.
I could give a million excuses for it like I �m rushed off my feet or am tired but in the end it �s just plain laziness.
Thanks again for your opinions. They all count.