Stop reading this sentence and picture a school; in your mind enter a classroom where class in underway and look around. See the teachers in the room, see the students, imagine what they are doing. If you didn’t play along with the preceding sentence, recall a movie or television program you watched in which a classroom, teaching, and learning was portrayed.
It doesn’t matter the age of the students you imagined; I predict there were certain elements that came to your mind. First, the teachers were likely lecturing or leading other activities they had selected and planned. This seems reasonable. Teachers are experts in their field (or sufficiently expert to have fooled whoever hired them); they are responsible for looking at the curriculum, deciding how best to teach it, carrying out their plans, then having the students demonstrate they actually learned what they were taught.
Second, there were indications of the curriculum. Perhaps students were reading textbooks, perhaps they were solving problems, but there was some content they were expected to learn. That curriculum was created by someone or some group charged with deciding what those students should learn in that particular classroom. Third, the students were probably going to be tested on what they were studying. Performance on those tests is thought to the correlated with learning; those who perform better learned better. These are the customary elements of our concept of education; teachers provide instruction, so the students learn the curriculum, and they assign grades which reflect the degrees to which the students learned the curriculum.
There is little inherently necessary about any of this. Increasingly, learning science is finding much that we assume to be true of school is not.