Is this a pen?

"We studied English in high school, but when I hear them talk in films or on the subway, it's like they're speaking Martian. They never want to know, 'Is this a pen?'"

David Mitchell, Variations on a Theme by Mister Donut

It's the start of a new school year so a few weeks into the book, seven-year-old learners of English will soon be inquiring "Is this a pen?" But as the quotation above indicates, this is a question it's quite unlikely they'll be faced with in real life - most speakers of English recognize a pen when they see one and have no need to ask. 

In fact, a quick search of the British National Corpus, returning 50 random results for the phrase "Is this" doesn't contain a single example of "Is this a [singular noun]?"

The most common types of question in the 50 examples are:

• five examples such as "How is this done?", with this used for anaphoric, not exophoric reference
• two examples of "Is this the ..." as in "Is this the start of a new series then?

The great majority of the examples showing how "Is this..." is actually used in authentic discourse are affirmative statements where "is" and "this..." happen to co-occur in cleft sentences such as:

• It is this state that fascinates particle physicists.

It's a relatively simple matter to avoid teaching the obviously useless vocabulary contained in coursebooks for beginner students, but we should take an equally critical eye to the grammar in our lessons.