On my CommonApp, I’d like to use teachers who have known me for only about a year for recommendations. I have some other options, but coincidentally, the subjects which I am doing best in and have the best relationships with teachers in, is the new teachers.
Would using new teachers give me a negative view or a disadvantage? Does the CommonApp even know if they are new?
If you have the best relationship with them, go for it. I assume a year means they were a teacher in your junior year? Using these teachers would not be a disadvantage, and the CommonApp does not know.
I think it is fine. If you just started with them this semester, that can be too short a period for them to have much to say about you. But if they are from junior year, you should be fine.
There’s a question on the LoR, how long have they known you. A full course year is fine. Just be sure these are teachers in the right cores, depending on your possible major. It won’t help to pick just those who like you best, if it means skipping ones who know your work in the actual subjects you hope to study.
No. “New” may mean new to your school with decades of experience elsewhere, or it may mean fresh out of college. Regardless, assuming the school/district is doing its job, a new teacher is still fully qualified.