40 When these considerations are taken together, a solid core of meaning emerges for "reasonable under the circumstances", sufficient to establish a zone in which discipline risks criminal sanction. Generally, s. 43 exempts from criminal sanction only minor corrective force of a transitory and trifling nature. On the basis of current expert consensus, it does not apply to corporal punishment of children under two or teenagers. Degrading, inhuman or harmful conduct is not protected. Discipline by the use of objects or blows or slaps to the head is unreasonable. Teachers may reasonably apply force to remove a child from a classroom or secure compliance with instructions, but not merely as corporal punishment. Coupled with the requirement that the conduct be corrective, which rules out conduct stemming from the caregiver's frustration, loss of temper or abusive personality, a consistent picture emerges of the area covered by s. 43. It is wrong for law enforcement officers or judges to apply their own subjective views of what is "reasonable under the circumstances"; the test is objective. The question must be considered in context and in light of all the circumstances of the case. The gravity of the precipitating event is not relevant.
 
59 Section 43 is Parliament's attempt to accommodate both of these needs. It provides parents and teachers with the ability to carry out the reasonable education of the child without the threat of sanction by the criminal law. The criminal law will decisively condemn and punish force that harms children, is part of a pattern of abuse, or is simply the angry or frustrated imposition of violence against children; in this way, by decriminalizing only minimal force of transient or trivial impact, s. 43 is sensitive to children's need for a safe environment. But s. 43 also ensures the criminal law will not be used where the force is part of a genuine effort to educate the child, poses no reasonable risk of harm that is more than transitory and trifling, and is reasonable under the circumstances. Introducing the criminal law into children's families and educational environments in such circumstances would harm children more than help them. So Parliament has decided not to do so, preferring the approach of educating parents against physical discipline.
   
60 This decision, far from ignoring the reality of children's lives, is grounded in their lived experience. The criminal law is the most powerful tool at Parliament's disposal. Yet it is a blunt instrument whose power can also be destructive of family and educational relationships.
   
62 The reality is that without s. 43, Canada's broad assault law would criminalize force falling far short of what we think of as corporal punishment, like placing an unwilling child in a chair for a five-minute "time-out". The decision not to criminalize such conduct is not grounded in devaluation of the child, but in a concern that to do so risks ruining lives and breaking up families -- a burden that in large part would be borne by children and outweigh any benefit derived from applying the criminal process.