Do colleges check for plagiarism in Letter of Recommendation?
You mean, for example if the teacher writes identical LORs for 5 different students?
No. Teachers writing hundreds, even thousands, of LORs over their careers are known to often plagerize their own prior creations.
Is plagiarism, just if the teacher copy the letter from another teacher, not if He/She use a own letter to write another one.
I use the same paragraph every time.
After I introduce myself and the student, I always write a paragraph on the course(s) I’ve taught the student to give context. And, for each course, that paragraph is identical. I’ve found a way I like to describe Algebra II & Trig, or Precalc, or geometry, and I reuse it.
But that’s it. Every single word I write beyond that is unique to that kid. I wouldn’t want some other teacher recycling a letter for one of my kids; I refuse to do so for any of my students.
That said, I’m sure that some teachers do as you’ve suggested-- check their files for another kid similar to this one, and pull up the same letter. And I’m not sure the colleges have the time or energy to check that.