Newswise — Sometime between the ages of 9 and 13, your mostly sweet-tempered child " the one who broke into a wide grin the second you walked into the room " will look at you and roll her eyes in response to reminders about picking up clothes or have rude outbursts over the least little thing.

This leaves parents wondering, "what happened?"

What's happened is your child has entered the "tween" years, and all of this is perfectly normal, said Dr. Liza Wilson, professor of curriculum and instruction in The University of Alabama's College of Education.

"The tween years are a time of huge physical, emotional and cognitive change," said Wilson. "Tweens are trying to figure out who they are and how they feel about things.

"Sometimes a negative attitude is a reaction to stress or disappointment. If your child had a fight with a friend, or is doing poorly in school, a flippant, 'so-what' tone may conceal fear or anxiety.

"There are a lot of times when things come up, everyone thinks it's nothing, but it's huge to the child. Don't downplay their fears."

While things like an obnoxious attitude are normal for tweens, Wilson said there are warning signs parents should look for when things go too far.

"If you see big changes like weight loss, a drop in grades, no interest in going to school, or withdrawing from friends, then you need to be concerned."

"If you cannot get an answer from your child, you need to check with other parents or their teachers."

Wilson said it is extremely important during these years for parents to keep the lines of communication open at all times.

"That's important because when they are ready to talk, you're there, and they don't feel like they have to 'approach' you."