I'm not even going to start on the stupidity of these sorts of 'plug and chug' assignments. This teacher is teaching something that goes beyond nonsense (just what is a "multiplication sentence" anyway?!?), and is just plain wrong! The phrase 'six times three' means the exact same thing as 'three times six'. Multiplication is (generally) commutative. Furthermore, the following should also be perfectly valid multiplication sentences deserving of full credit:
No wonder so many kids think they're "not good at math." They're being taught mindless drivel -- that doesn't even have the small benefit of being, at least, correct. And they've certainly never learned math.