@izzythepush,
Yes I good teacher can usually catch on. I remember when I was in college, I went to a college where it was mostly some sort of business major. I, unlike, most of the students in my class, loved to read and in one of my Literature classes, we were required to write a paper on a particular theme of the novel we were reading.
One of the classes after we submitted this paper, the teacher said - I know that most of the class plagiarized. I have years of experience and I can catch these. I will give you each one chance, if you cheated you can stay in the class now and write your paper. If you did not - you may leave. If you leave, however, and you cheated, I will fail you and report you to the dean.
There I am sweating - I know I didn't cheat - never read a cliffnote or whatever the heck those things are. I read the book and wrote by more than likely boring B paper - I was just a fair write.
Finally I thought - I know I didn't cheat I am going to leave - I got up and I was one of the very few students that left. Damn I thought that many students cheated!
I got my well deserved A- more than likely higher than I should have because it was an honest written paper.