The tween years are a critical time in the development of self esteem. Self esteem in children changes in four major ways during this period of life.
Self Esteem in Children Stops Being Naturally High
Until they reach pre-adolescence, kids tend to have relatively high scores of certain measures of self esteem. It doesn't take much to make young children feel good about themselves. When the tween years hit, however, self-esteem no longer remains effortlessly elevated. This change occurs for a variety of reasons, including tweens' increasing comparisons of themselves to others.
Variations In Self Esteem Appear
Since all young children tend to have high self esteem, it follows that levels of self esteem are similar from one child to the next. Therefore, when observing young children, it's almost impossible to tell which kids will maintain high self esteem and which will eventually feel badly about themselves. During the tween years, however, individual differences in self esteem begin to emerge. In other words, levels of self esteem begin to vary from one tween to another.
Self Esteem in Children Begins to Have Clear Patterns
The individual differences in self esteem that emerge in the tween years tend to be relatively stable over the following decades. This doesn't mean that a tween with low self-esteem will always have exactly that same level of self esteem as she does at that moment. What it means is that a tween who has lower self-esteem than her peers will tend to continue to have lower self-esteem than her peers, even when self esteem in general improves during adulthood. In other words, tweens begin to show patterns of self esteem that will likely continue throughout their lives.
For Some Tweens, Self Esteem Drops Rapidly
Unfortunately, as tweens' levels of self esteem begin to diverge, some tweens' self-esteem drop precipitously. Not unrelated, depression also makes it first full-blown appearance during these years. Girls who experience early puberty may be particularly prone to both low self esteem and mood issues. Thankfully, there are some things parents can do to help their children maintain healthy levels of self-esteem.
Harter, S. Developmental and Individual Difference Perspectives on Self-Esteem. In Handbook of Personality Development by Mroczek and Little (Eds.), pages 311-334. 2006. Mahwah, NJ: Erlbaum.
McAdams, Dan, & Olson, Bradley. Personality Development: Continuity and Change Over the Life Course. Annual Review of Psychology. 2010. 61: 517-542.