Why do young high school teachers make me uncomfortable?
Young teachers sometimes mess up the boundary between "teacher" and "peer," and that can make everyone uncomfortable.
The way I'm understanding it, you respect your teachers and you want to respect your younger teachers as well. You want them to be authorities, not friends. But they don't look like or sound like your other teachers- they sound like you, and you know that you're too young to know anything worth respecting.
Here's the thing, though: age does not automatically equal knowledge and authority.
At some point, you will probably have bosses who are younger than you. You may be the boss of people older than you, the same age, and younger than you. You may be required to take authority over a situation that you are not prepared for. Imagine how you would do that.
Your teachers, even the youngest of them, spent several years gaining the specialized knowledge and experience necessary to manage a classroom and teach their subjects. They are the authority in their classroom.
You really don't have to be friends with your teachers if it makes you uncomfortable. But, I suggest that you ask them about their schooling and why they chose to become teachers. I guarantee you will learn some things that you will respect about them.
I'm 22, I regularly teach high schoolers, and I love my job even when it's difficult. If you feel uncomfortable asking your own teachers, go ahead and ask me!
(Edit: I forgot to say that, young or old, no teacher should cross the boundary of romantically pursuing a student. Please feel free to take your specific concerns to another teacher or school administrator.)
Part of the problem is that often our society discounts the abilities of younger people (and the elderly). Partly the teacher is not setting proper boundaries. Often younger teachers want to be pals, buddy-buddies, instead of being the teacher. A teacher can be a buddy or an authority figure, not both. I think you feel the inconsistencies and you are reacting to it. A young person can be a teacher and a good one, but her or she really needs to find a comfortable place between authority and friendship.
Young teachers are so close to the age of their students that they could almost see each other as peers. That does not work in a school environment. It is easier to see an 18 year old student becoming involved with a 23 year old teacher than with a 50 year old one.