Regarding PHP, if you want it as a rite of passage it should come
after writing software in better languages with better tools. PHP-first means bad-habits-first.
C imposes similarly rigorous proving grounds for developers, but without pushing new developers into bad habits that would come back to bite them later. If you want people to start with more requirements for hard thinking about how to not build a deathtrap, choose C instead.
As for the benefits of rendering server-side, they are legion, and most important among them is the fact that pushing everything to the client-side part of the system means not really knowing what your code will do in the wild, imposing whole new classes of frustration on users, and piles of other horrors. Yes, we could benefit from falling back on far more default-server-side technologies and using JavaScript only where it's needed, I think, for the sake of the users first and foremost.
JavaScript is great for some things. It's terrible for others, and all too often trying to use JavaScript for everything means coupling the wrong tools for many jobs together with the wrong place to run code, too. Even when I enjoy JavaScript work, the simple act of checking online documentation for the JavaScript tools I'm using ruins the whole experience for me as I realize how we're punishing our users when we don't think about how we're using JavaScript from a user's perspective.