S.P.
I am a middle school teacher, but I couldn't help chiming in -
I guess I'm surprised that you like K because "there aren't as many skills to teach." My feeling is that if you don't want to teach skills and don't want to push the children as far as they can go or don't want to worry about "low kids," then you might not be enjoying the entire field of teaching anymore. It might be time to think about doing something else if you've lost your passion for teaching.
Obviously, I could be misreading the entire situation - not knowing you and only being able to read 1 paragraph, it could be that you really are just bored and need a new challenge. In that case, I highly recommend looking at the upper grades. You may find the challenge stimulating and it may recharge you. 4-6 graders are so fun - they're more capable of abstract thinking and reasoning, they have lots of fun little quirks, etc.
For me, my niche is truly middle school. I adore 7th and 8th graders. I think they're the most fun, wonderful, stimulating people on earth. I can't imagine having to come to work everyday and not feeling that way. They are passionate and funny, capable of really thinking and reasoning in meaningful ways, they surprise me all the time (even after doing this for 10 years), and they are ready to tackle tough issues and tough concepts. What's more, they still love and need you as much as they did in Elem. school.
Good luck!