How would you punctuate this sentence

The town where my father grew up has a population of only 1,222.

I need someone to let me know what commas are needed, if any.  I think the sentence should be this way:

The town, where my father grew up, has a population of only 1,222.

"Where my father grew up", is a nonessential clause, therefore, needs to be seperated by commas.  My instructor says not so, that information is needed for the sentence make sense.  Thanks for any help.

Barbara is correct. If you were saying "Springfield, where my father grew up, has a population... " you would then require commas, because your reader may not realize that Springfield is a place, and so the defining clause explains this. But "the town where my father grew up" is one idea: nothing is explaining something else.