I’ve been asked this from time to time, and I see if asked on facebook groups and other fora like the Chronicle of higher education. The basic answer is no. You can probably earn a professional doctorate (Ed.D., SLPD, etc.) while working part-time or even full-time. But, it’s different for a Ph.D. (at least if you’re a full-time student).
The goal of the Ph.D. is to develop expertise in an area of study, learn to do research, and to contribute to the literature in the area you are studying. You learn about teaching and how to develop and organize a class.
The Ph.D. is not just about taking a bunch of classes and calling it a degree. It’s really more of an apprenticeship. Classes are just there to learn some of the tools and content that you need to do the work. But, the work is most important. One way to think about this is to think about the MA training for SLPs. In such programs students take classes, write papers, read and they also do clinic. They do clinic each semester or quarter they are enrolled in the MA program. Usually this takes some 10-30 hours/week. They are learning the practices of being a speech-language pathologist. The Ph.D. is similar. The practices of being a researcher and teacher are to conduct research and to teach.
Ph.D. students have to learn to read the literature, identify and develop a research question, design a way to answer that question, conduct the research, evaluate its outcomes, and write it up. To be successful in a tenure track job you have to be able to write 2-3 (or more) papers a year. So, this aspect of Ph.D. training is critically important.
In the HABLA lab, Ph.D. students are involved in all aspects of on-going research. They may help to collect data, plan a study, do analyses, help write up papers for publication. They need to do at least one rotation where they take the lead on a paper (propose the question, find the data to answer it or collect data, write it up– typically with input from Lisa or me). For this study they are the first author, and Lisa and/or I may be co-authors. Others may also play roles in helping develop the question or do analysis or write up part of the discussion so they would also be co-authors. But, the lead author is the one who takes the lead in question development, invites others, writes up a large portion of the paper, and does the final editing so that it all flows. They also deal with reviews and most of the revisions.
In addition to taking the lead on a research project in the lab, Ph.D. students may also be involved on other projects. They may have a more limited role such as running and writing up results, or methods, or other intellectual contributions. These all can earn authorship. I think that students at any given time should be in charge of 1 project and have a secondary role on 1 or 2 others. As they go through the different roles, they are refining their skills (and building that CV).
But, you can’t do this if all you do is go to class and then to work. You have to be around and involved to be invited to participate. You have to be around when we’re throwing ideas around. If you’re not, I think you miss out on learning the essentials of being a researcher.
Teaching is not much different. You need to do it not just learn about it. Usually, Ph.D. students will be a TA one year (sometimes more, other times less). But, through being a TA students learn to plan a class, evaluate learning, develop grading rubrics, plan a series of lectures and activities. If you aren’t involved in these things then it’s difficult to demonstrate teaching experience.
So, I don’t recommend working full-time while in a full-time Ph.D. program, you miss out on too much of what you need to launch a successful research and teaching career.