A young person between the ages of 10-14, give or take.
Also the beginning stages of puberty, so expect your sweet little elementary
schooler to begin changing in the most horrible of ways. Most
middle schoolers will struggle with puberty, some more than others. Most give in to their hormones and act with carnal instinct, becoming obnoxious foul-mouthed babies with no respect for anyone-- this is due to the fact that they are confused and have absolutely no idea what to do with all of these new emotions and are trying to compensate this "weakness" by acting like brats.
Other middle schoolers at most will develop some lip, but are able to control their urges. When they go into high school they are generally more prepared to deal with high school, which is to be described almost as a breeding ground.
Middle schoolers are NOT to be confused with
highschoolers. Middle schoolers are still in the "opening" stage of adulthood, whereas highschoolers are rushing through the "blooming" stage and "settling" stage. Middle schoolers are very experimental as they begin trying to find their identities, not knowing that identities are not found but developed.