The last words of lines one, two and five must rhyme.
Each of these lines must only have eight syllables.

And the last words of lines three and four must rhyme.
Each of these lines must only have five syllables.

1. There once was a teacher from Cork        (This line has 8 syllables. I, 2 and 5 rhyme.)
2. who was mad about the band Bjork         (This line has 8 syllables  I, 2 and 5 rhyme.)
3. so crazy was she                                      (This line has 5 syllables. 3 and 4 rhyme)
4. That she made CD                                   (This line has 5 syllables.  3 and 4 rhyme)
5. And gave it to Bjork, like a dork.             (This line has 8 syllables  I, 2 and 5 rhyme.)

image source