PhD in Science Education
About two years ago I received my PhD in Science Education from the University of Maryland, College Park. Overall the process took me about eight years since I was teaching high school at the same time. Working on a science education PhD while holding down a job pretty much means that all you think about is teaching and working on you doctorate. It was helpful to be in a school while taking education courses but at the same time exhausting.
For the last two years I was able to teach a 60% course load at my high school while collecting data and then writing my dissertation. This was essential since it give me the time I needed to focus, analyze data, and write. I'm not sure I could have done it without that arrangement.
Classes were the easy part of the whole PhD in science education program. In general they are very clear in what you have to do and when. Once the class is over you move to the next one. When you get to writing your dissertation things are more open ended and it's on you to keep things moving forward.
For people considering as science education PhD understand that it is a long road. At the same time I believe I'm a much better teacher, writer, and problem solver as a result of the process. A doctorate also opens doors to new opportunities and experiences.
Perhaps the most important advice I can offer is to spend time and find a good advisor (ask around, take your time). It's most important once you begin your dissertation proposal and shift away from coursework to doing research. This is a big deal and seems to be a huge factor in who ends up being able to put Dr. in front of their name.
You can type in "Doctorate in Science Education" or "PhD in Science Education" and the name of the state where you will likely attend to find programs in your area.