Unit 6: Elimu. Education > Lesson 6: Shule ya ufundi

The title says "Shule ya ufundi" and right below it, the first line of text says "Shule za ufundi." Which is correct?

ya is singular and za is plural

Agreed. So why is it singular in the title, and plural in the text?  

I have no idea, because it's not our passage. Titled vocational school, with header vocational schools; inconsistent perhaps, but not grammatically incorrect

Different topic:

  In the sentence, "Katika shule za ufundi wanafunzi hufundishwa ufindi chuma . . . " I thought the "hu" prefix would make it negative?

Hu can also mean habitual, as it does here. It depends on context.