Not to call you wrong, but,
Theodore Kaczynski (unabomber) not Islamic
Oklahoma Federal Building bombing (McVeigh doesn't sound Arabic to me)
Centennial Olympic Park bombing - Eric Rudolph. Again, doesn't sound Arabic to me.
The list goes on and on. What have you got? 9/11 and the Boston Marathon bombing? If you want to use any random shooting of 2 or 3 people by some member of Islam - which are all reported to death when they occur, then you're going to have to balance that against all the other mass shootings by mostly white males.
I agree with you, that on a country by country basis.
Most particular countries, have a mixture, of terrorist types. But when you look at the news (since 9/11), on a world wide scale.
One regularly gets the impression, that a particular religious group has lots of terrorists, who desire to try to kill many westerners, and other people, around the world.
If you just catch a bit of the news. "country xyz..ia, a suicide bomber has just blown up 20 people. Thoughts of it being that particular, religious group, immediately spring to mind. From what I have heard.
Anyway, one can find a live, terrorists, bomb just about anywhere, potentially. We should always be vigilant.
Initially, it was an innocent mistake by the English teacher, and a reasonable one as she was acting out of concern. But, as soon as he showed/told what it did, it went beyond innocent.
It's reasonable for the Police to take time to decide what to do. They had found a device, which could, at the very least, be seriously considered as being a fake bomb device.
If it is true that the boy was being difficult (uncooperative), when the Police asked questions, about the device.
Then they are within their rights. To take him in for questioning and further processing.
In some respects, the boy has been lucky.
If they had evacuated the School, and brought in swat and/or bomb disposal teams. It could have hit the headlines. If they had reason to believe that he did it on purpose (fake bomb).
He could be in very serious trouble now.