As others have said, it really depends on what you like to do. If you want to aim at being a school principal, then school administration. Think about what the principal and assistant principal do at the schools you have been involved with to get an idea of what they do. It ranges from personnel management, through budgeting, through a thorough knowledge of education law, to dealing with parents.
If you want to be in huge demand in the classroom, then special education. If you like dealing with bright kids then gifted and talented. If you are interested in steering kids in the right direction, or working with troubled kids, then counseling.
You can also get a Master’s in psychology if you want to work at making life better for special ed kids without necessarily staying in the classroom. You would be involved in ARD meetings, testing kids to determine if they need services and what services might they need, and possibly even setting policy for a school or a district in regard to kids with special needs.
And finally, if you want to move into middle school or high school teaching, then degrees in science or math can be very useful. I know in Texas we are desperately short of folks in those fields.