This is one of the most common questions in pedagogy. Sometimes it reflects a lot of anxiety.
This question is similar to this one: how to be healthy? It’s quite obvious that there is no straight answer. There are lots of things to do in order to be healthy. You need a good hygiene. You need some good daily routines, like enough sleeping time or a well-balanced diet. You may need medications sometimes. If one of your organs fails dramatically, you’re dead. It doesn’t matter if you loose your brain, or your liver, or your heart, or your kidney. The result is the same. Your need all of them in a correct shape.
So, let me rephrase the initial question: why are the students not motivated? Curiosity is natural to children. A 5 year old child normaly spends a huge amount of time asking questions. Why do cows have horns while horses don’t? Knowledge is one of the most profound desires of the human species. It’s as vital as food. Having to explain how to motivate students is equivalent to explaining why people loose their appetite. There may be a lot of reasons, as the are lots of diseases. Let’s see some of these.
Perhaps the lesson is too fast, and the pupils can’t catch it.
Perhaps it’s too slow, and they get easily bored.
The lesson can be too hard, and the students are discouraged.
The lesson can be too easy, and they don’t see its utility. It’s tempting to lower your expectation when you see that a class doesn’t work well. However, sometimes, it proves to be an error, and the students work even less! You can easily figure out why. There is no longer enough interest in the lesson to trigger the work of the students. This issue is common in any work environment, even with adults. You can easily find volunteers for a charity if you have a regular activity, but you will have to spend much more energy if you want people for one single occasional service, because everyone has already a schedule. Everyone has other things to do. The pupils are the same. If the English teacher has too few demands, they will choose to focus on mathematics or anything else. They prioritize their efforts according to the teacher’s expectations. And it’s a good thing! It’s a sign of intelligence!
Sometimes the adults are too judgemental.
Or they give the impression that they don’t really care about the children’s achievements. It doesn’t matter if that impression is true or false. The impression itself is enough to annihilate the goodwill of a child.
In the same way, the teacher can give the impression that accuracy doesn’t matter. If he accepts any kind of answer and praises any attempt from the children, he makes them careless and futile.
On the contrary, if he tracks every mistake, they will think that their efforts are useless and that the teacher punishes them for trying. “We’re never good enough!” is a common cry of dispair.
As you can see, motivation is mainly a question of balance. A teacher must adapt his lessons to the specific needs of his students. Not to say that he should flatter them or have an invasive knowledge of their psyche. But he has to keep an eye on their reactions and understand the circonstances that make the lesson easier or harder. After all, that’s why we pay teachers. If not for their adaptability, we could replace them by computers… or books.