Firstly let me say that the teacher was right to confiscate the bracelet, but totally wrong to bin it. Even if it had little monetary value, it had a lot of sentimental value.
But, I also agree that any parent who thinks their child has been badly treated by a teacher needs to address the situation calmly and sensibly - simply because that is the best way to sort things out.
In the past, friends of mine have gone into school, all guns blazing, to complain about something, only to find that their child has not told them the whole story and was, at least partly, in the wrong - and the parent has come out feeling they've made a fool of themselves.
If you have a problem, of course you have every right to discuss it either with the teacher concerned, or with the school. Generally it is better to go to the teacher first as most things can be best sorted out this way, and going over a teacher's head can cause more problems. Obviously if the situation isn't adequately dealt with, or if you are still not happy with the solution, then you take the issue higher - and if you do have to go higher, you can show that you have done your best to deal with the situation through the right channels and haven't got anywhere.
In this circumstance, I would, as has already been suggested on the thread, go and ask the teacher when the confiscated bracelet will be returned. I would make it clear that I backed the school up on its rules about jewellry, and just wanted to know the full story.
When and if the teacher told me that the bracelet had been thrown away (or lost - if I was a teacher, I'm not sure I'd want to admit to a parent that I'd thrown away some jewellry), then I would ask what the teacher intended to do to rectify the situation, and would explain that the bracelet had been a christmas gift that I had struggled to buy and could ill-afford to replace. If I didn't get a satisfactory response from the teacher, I would then go to the Head.
With regard to the plagiarism issue that has been raised - if scienceteacher (or any other teacher) has repeatedly told their pupils not to plagiarise, has shown them how to use the resources correctly, and has warned them that plagiarised work will be binned, then I wouldn't complain if my child plagiarised work and it was binned. A secondary child should be old enough to know that actions have consequences; and if a teacher issues a warning about the consequences of plagiarism, then they do have to carry it through, otherwise the pupils will take advantage next time.
Of course the teacher does have to be careful that any punishment they threaten is reasonable - does anyone here remember the teacher who threatened her noisy class that the next person to talk would be gagged with parcel tape - and who carried through on the threat!!! She lost her job, and rightly so.