Use of force (violence) is the tool the government uses to make the population comply with their authority. The state wants people to accept its continuation because it is a self perpetuating entity, it is in the interests of the people who work within it and it is the means by which the controlling oligarchy suppress the people and gather their tithe.
Use of force in schools conditions the population, (including teachers, parents and pupils) to accept this paradigm as normal and acceptable.
Schools are set-up in such a way so that the intuitive, inquisitive, independent spark is stamped right out of children and replaced with unquestioning capitulation to authority. Many youngsters happily fall-in with this mantra and offer no resistance. Some fail to engage and must be broken-in or are rejected as scholastic misfit failures.
If state schooling used a 'student centred' means of development, where, rather than ramming a curriculum of broadly useless topic based information down their throats, they help students to develop by following their interests and taught them the basic tools of learning; the problem would be, for the state, that too many students would become empowered as adults with intellectual ability and start to question and want to change everything. They would soon question the need for a state at all and with that include the desirability of the state's control of children's 'education'.
Note: The keen eyed reader may note under my little icon I include the tag line "We are not children". I do not mean any disrespect to children by this because I believe children are intensely perceptive and intrinsically pure of thought - I would like to still be like that. I mean that the state treat us like children and train us to remain immature. We do lose many of the the miraculous virtues children possess but are failing to successfully gain all those qualities that should arise with maturity: wisdom, gravitas and so on. This is desirable to the state - this is the deliberate intention of the conditioning we are subjected to. Myself included.