Hojo Soun plan was simple, take over the world.  But the rate of which information travels in the modern world is too fast.  At the urging of her host mother, Hojo attends the local school in which she realizes that to take over, you have to start small.
In other words, they're controlling 
the school by force.
O sea que están intentando 
controlar la escuela a la fuerza.
O sea, que están intentando 
dominar el instituto por la fuerza.
Em outras palavras, eles controlam a escola usando a força.