The issues here need to be viewed dispassionately, without anger. You may be too close to do that. One, is the official rule, without regard to whether other teachers enforce it or don't, that you are not allowed to have phones in class?
If that's the rule, then the teacher is justified in taking it from you at that time. Two, if you believe your teacher and her child damaged your phone, that's an issue in which to get your parents involved. The cost of a smart phone is well within the bounds of a small claims court.
You will need to amass witnesses to testify the phone was not cracked, that the teacher took it from you during class, that she slammed it down, that her child was in the lounge, and that the child had the phone with the crack. IMO, your parents should also contact the administration about this teacher's over-reaction and damage of property, even if that property should not have been in the classroom. All that said, though, your having it when you should not have was probably the catalyst that led to this mess.
That sounds so serious you need to tell your parents. Only with their backing will you be able to make a complaint. If they believe you get them to come to the school & explain to them what happened, & to get your phone back.
I hope you're normally good & well behaved in school because it will help your case a lot if you are. But if you're normally disruptive you'll have a much harder job. But assuming you don't get your parents' backing you need to do all you can to publicise this event.
So first of all politely go to your principle's office & report it. Have someone calm & respected by the teachers come with you to back you up. Have as many people as possible come & back you up.
Maybe ask to be moved from that class to the class of another teacher you can trust because you no longer feel safe in the company of that one. Then tell as many teachers & support staff as possible. Don't be rude or aggressive, just be upset & worried & distressed.
Then get as many people as you can to spread this story round the school & the neighbourhood. So you could talk about it on Facebook or Twitter. Talk about it everywhere that will get the story out in the public domain.
If you have access to a school website or a school Facebook page try & publicise the story there. If nothing looks like it's being done you may have to resort to more desperate measures. Like call out in a whole school assembly Miss (teacher's name) stole my phone for no reason, everyone PLEASE tell your parents, everyone, don't let her get away with it, PLEASE PLEASE tell your parents & ask them to ask the school about this, PLEASE.
An empassioned appeal like that will certainly get the event talked about & some might even tell your parents, then there's a chance some of those parents may get to call the school. Then it becomes a damage limitation exercise for the school.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.