Problems sharing are typical

Q. What's the most effective way to get young children, ages 2 and 3, to share, and what should I do when not sharing escalates into violence? I work with this age child in a day care center and this is my biggest problem.
A. It is not at all unusual for children to have problems sharing until well into the fourth year of life. Why non-sharing is typical of children below age 4 is anyone's best guess, mine being that during late toddlerhood, a child begins to grasp the concept of private property. "Mine!" is the natural consequence of this realization. Furthermore, refusing to share enables the child to exercise a greater degree of control over his immediate environment, including his playmates, while at the same time making a clear assertion of his identity.
Unfortunately, some of these non-sharers tend to become aggressive toward other children who try to play with "their" toys. Needless to say, their aggressive outbursts are not consistent with standard rules of engagement, much less the Geneva Accords. The toddler is undersocialized; therefore, when he/she strikes out aggressively toward another child, the assault is likely to look distinctly savage to the civilized onlooker.
The first problem -- simple, garden variety non-sharing -- can be slowly solved by parents and other caregivers who are firm in their expectation that children share and who provide the disciplinary structure within which sharing can be learned. One way to do this is to use a simple kitchen timer to signal when the toy in question has to be exchanged. In most cases, once children have learned to take turns in this fashion, they begin spontaneous sharing in almost no time at all.
Aggressive answer
The answer to a toddler who hits, kicks, pinches, and bites is to immediately remove the child from the playgroup, even if it's a group of two, until he/she is ready to apologize and share. If an aggressive incident occurs twice in the same play session, I recommend confining the child, even at the tender age of 3, to his or her room for the remainder of the day, along with an early bedtime. If it occurs in a playgroup, I recommend separating the child from the other children in the group for the remainder of the session. To those who would say that separating a child from the group from, say, mid-morning (when the second incident hypothetically occurs), until his parent picks him up at the end of the day is too much, I respond thusly: If one wants the aggression to stop, which should be everyone's aim, and quickly, then the consequence must be memorable. It must create a strong mental imprint that will hopefully begin to inhibit aggressive outbursts. Meanwhile, adults should definitely use the opportunity to counsel the child on non-violent means of handling similar future situations.
The answer to a toddler who hits, kicks, pinches, and bites is to immediately remove the child from the playgroup, even if it's a group of two, until he/she is ready to apologize and share. If an aggressive incident occurs twice in the same play session, I recommend confining the child, even at the tender age of 3, to his or her room for the remainder of the day, along with an early bedtime. If it occurs in a playgroup, I recommend separating the child from the other children in the group for the remainder of the session. To those who would say that separating a child from the group from, say, mid-morning (when the second incident hypothetically occurs), until his parent picks him up at the end of the day is too much, I respond thusly: If one wants the aggression to stop, which should be everyone's aim, and quickly, then the consequence must be memorable. It must create a strong mental imprint that will hopefully begin to inhibit aggressive outbursts. Meanwhile, adults should definitely use the opportunity to counsel the child on non-violent means of handling similar future situations.
In the final analysis, however, nipping behavior of this sort in the proverbial bud requires parents and teachers who absolutely will not tolerate it. So, yes, when aggression takes place at preschool, and the child is 3 or older, parents should follow through with a punishment at home. Some research indicates that when parents do not take strong disciplinary action concerning aggressive behavior when it first emerges, the problem can grow from molehill to mountain in no time at all.