Yes, absolutely. It's unfair and violate many issues, such as copyright, etc. Students should gain new knowledge at colleges and universities, not steal other people's thoughts. Besides, students have to learn how to make quotations and citations properly. Also, usage of special plagiarism detection tools (For example, PlagTracker or Unplag plagiarism checker) and running written paper through these engines could lead students to an awareness of the originality of their work. If it isn't original enough, the student could correct it and write another paragraph, insert proper quotations, etc. So, fortunately, there are ways to prevent plagiarism in schools.
Yes, they should. It is unfair, especially for those who will be uncredited for, or their academical abilities. It's been highly stressed throughout school not to plagiarize. Any theft, even cheated should have consequences. You shouldn't have to rely on others to do your own work. It is unfair and dishonest.
No one should be expelled for an assignment. If a student copied work, Then he/she should just fail the assignment, Not be kicked out of college, Going into debt and having almost no chance of getting a degree. Plagiarism is bad, Yes, And the person should be punished. But expulsion for an assignment is simply too far.
If an author has written it on the internet then it completely fine plus if it is a brand new topic for a child then they are allowed to have a kick-starter and not be punished by failing just because they forgot to write a site or the author.