Zoey 101 did NOT end because of Jamie Lynn's pregnancy
A common misconception is that people think that Zoey 101 was cancelled because of her pregnancy, but it's simply not the case. the show had already wrapped production of Season 4 in mid August of 2007, and Jamie Lynn didn't inform the crew of the show until two months later in October 2007, while the public was informed in December 2007. Keep in mind that the last episodes of Season 3 were still being aired at this point up to January 4th, 2008 (which is when "Goodbye Zoey" aired). Season 4 didn't start airing until January 27th of that same year, though there were many angry parents that did not want that season to even air because of the teen pregnancy situation that went on behind the scenes.
Also one more thing, it was NOT Dan Schneider either, a lot of people speculate that he was the cause, and even though yes he is a creep, that information is false. it was her boyfriend at the time Casey Aldridge.