Hey there!
Yeah, this is a tricky one. Usually for people who are a few years out, I’d still encourage them to contact their old professors - they may not remember you, but you may be surprised; some of them may. (An old student of mine from about 10 years ago reached out on LinkedIn a few days ago and I immediately remembered her.) Usually in these cases, I would tell the candidate to send that professor their resume, their statement of purpose, and a little blurb about what they’ve been doing in the interim.
I think you have the right idea in trying to take some summer classes to get some more recent feedback from professors who know your work - and since you have an MA, you want to take graduate-level classes with graduate professors. To give yourself the best shot, you may want to delay this by a bit so that you can take in person classes, but there are ways to get close to professors virtually too depending on the size of the class.
More importantly, though, you need research experience to be competitive for a PhD program in sociology. If you haven’t been doing research with a sociology professor/PhD holder recently (like within the last 5 or so years) and don’t have a professor/sociologist who can testify to your potential to succeed as a researcher in the field, you’d be less competitive for PhD programs in sociology. Most competitive applicants are going to have ~2-3 years of part-time experience doing that. So rather than thinking about applying in the fall, I would think about this as a period of time when you strengthen your application portfolio.
First, I would say you should consider programs in schools of education rather than (or alongside) pure sociology programs. They’re going to be more forgiving of someone whose primary previous experience is K-12 teaching. There are PhD programs in Sociology of Education - for example, Teachers College at Columbia, UC-Irvine, Stanford, Harvard, Chicago all have one. Since you want to study education + race & class, that may just be a better fit for you anyway; you’ll be in good company with lots of former teachers.
As for a writing sample - you may want to sign up for a graduate class that has a seminar paper requirement. That can help you get a letter of recommendation AND can help you write and get feedback on a paper to submit as a writing sample.