TRIGGER WARNING: discussion of child abuse
I think when people hear the word "child abuse" they think first of the worst cases you hear in the news; children who are so badly beaten or neglected, they get taken away by child services, or even die at their hands of their parents. Or they think of sexual abuse. However, that leaves a whole lot of grey area between the worst cases and good parenting. There's a lot that happens in between that is still abuse and we are so reluctant to talk about it, that children who don't see themselves in the extreme cases don't even know they're being abused. Also, friends of yours who are abusing their children never get called out because, "it's not *that* bad."
So let's talk a bit about what abuse is and what is can look like. Keep an open mind, as uncomfortable as it makes you, because it can mean that you have been abused, you may have abused your children, or you may even be friends with a child abuser. What is important is what you choose to do with that information.
In my case, I was never sexually touched or physically abused by either of my parents. However, I still acted enough like an abused child that doctors and teachers asked me if anyone had "touched me" or hit me. So of course, I said, "no." No one ever thought to ask me, "does mommy call you an idiot?" because then I could have said "yes." I never thought to offer that information because I didn't know it wasn't normal to be called an "idiot" on a regular basis.
So there's your first example: an abused child can act out at school, or they can be very quiet or "repressed" (as I was described). In my case, I kept quiet to myself because that was the safest method of behaviour at home, but I also appeared "happy" at school because it was my refuge from home. I could be somewhat freer at school. I did well at school because the praise I got from teachers concerning my marks was the only positive attention I got to feed my self-esteem, and I knew school was my ticket out of the house one day.
An abused child does not know they're being abused because the way they are treated by their parents is all they've ever known. It's not until much later, when I saw how other families live, that I developed an awareness that something was wrong. I knew I was not happy, but I did not know why. I thought there was just something wrong with me that I must deserve it.
(It helped as well that my parents did not like me having friends over or going over to friend's houses, so that isolation kept me from knowing I was abused)
I have heard parents defending their poor/abusive treatment of their children as "infrequent" or "maybe once or twice." However, abusive behaviour doesn't have to be a daily thing for it to be abusive. Abuse can happen daily, monthly or at random spontaneous outbursts. Unfortunately, the frequency of it is not a measure of the damage. Abusive acts are still abusive even if it only happens once. If it happens once, there's the potential for it to happen again. The long term effects or damage on a person do not change based on frequency. It's still damaging.
For example, your house can burn down once and it's pretty devastating. You probably live with the fear that another fire could happen again. That's how a child feels after the first time they've been abused - living in fear it will happen again.
I will use Part 2 to go into more detail about abusive acts that people don't often think of as abuse.