To lie is to assert falsely, though what exactly it is to assert falsely is unclear. It probably doesn't mean to assert a falsehood. Some say it is to assert what one doesn't believe. Some say it is to assert what one what one disbelieves. Some say that it is to assert without believing that what one is asserting is true. Some add the condition that it is to deceive. But a common denominator in all of these is that a lie is a special kind of assertion.
But suppose I deliberately and deceptively start spouting pseudoscientific nonsense to my students, in aid of some argument I am pushing—nonsense in the literal sense of the word, namely stuff that has no meaning at all. I tell my students: "The paramorphogenophilic field surrounds us all and photons are submorphizations of that field." I am not lying, since I am not asserting anything. If it were the case that I was asserting something, one could ask: What am I asserting? And the only potentially possible answer would be: "He is asserting that the paramorphogenophilic field, etc." But this answer is itself nonsense—nonsense in indirect quotation renders the whole sentence (if one can even call it a sentence) nonsense.
So I am not asserting. But what I am doing is surely just as wrong as lying and for the same reasons.
What then are these reasons? It is not the production of false belief. For the students would not form a belief, at least not directly. There is no belief that the words which they then could parrot on a test express. The best account here seems to be that of Jorge Garcia's account of lying. I am inviting their trust and simultaneously breaking it.