After I told a class that Pascal (actually, any modern programming
language) is not context-free, a student challenged me, showing me what
was claimed to be a context-free grammar for Pascal (or some other
programming language) in the back of a programming book.

What is going on?

The answer is that a modern programming language has what is called an
"underlying context-free grammar," a CFG that generates every string in
the language, but lots more strings besides.  For example, the following
"program" would be generated by that grammar for Pascal:

  program wrong(input,output);
   var
    i:integer;
   begin
    j := 5;
   end.

Do you see why it is wrong, and why the grammar would generate it anyway?
And, if the grammar is "wrong," why is it mentioned in textbooks?