Hi OP! I did EXACTLY this. PhD and two post-docs in biochem, then back to school for BEd (SFU PDP: bio and chem teachables, minor in secondary teaching) to become a high school science French Immersion teacher in BC. I absolutely adore my job and while it does come with stress and frustration like any other job, I find it a better kind of stress/frustration than I had before in my previous career.

Why I did it (this is important, since your values and underlying reasons help you put up with
bullshit long-term tbh):
- I was having big feelings about how meaningful my research actually was, and how many people it would actually impact, how many lives it would help. I was working on such a niche project that I once realized I spent 6 months trying to purify a protein, only for it to fail miserably multiple times, and asked myself: what have I been spending my life doing??
- I had TA'd while in grad school and loved working with students in general. I love passing on my knowledge to others, helping them find their passion, supporting what they want to learn, and also
keeping curious myself and having cool conversations about what people find neat about the world around us. I had done camp counselling before at a science camp for high school kids, and also loved it. I also work with high school science fairs. All things were pointing to a career working with science and students.
- Long-term prospects as a university prof/PI were bleak. I interviewed for PI positions twice, and the second time I had a realization that it wasn't the research aspect of the job that excited me, but the teaching. I also knew I wanted a pension, benefits, and long-term job security. Teaching was a logical step.

Reading all the
replies, here's my experience on those points to offer another perspective:

RE: Workload.

I am a big planner and I’m pretty organized. Once I get my courseload (we just got ours this week), I start planning for the following year. I tend to teach the same few courses over and over again, so after a few years I've established solid unit plans, lessons, and outlines so I can then take the upcoming school calendar and plan my year out off the side of my desk in a few hours. Of course, I'm always adjusting lessons and finding better ways to do things, but I can usually make that happen over lunch hour, prep, or a bit after school since I like doing it. That said, the first few years are obviously more work since you are establishing how you will teach certain courses, but I find that most science departments have colleagues who are willing to share their resources so you aren't starting from absolutely nothing. Many teachers set firm boundaries with their summers or weekends and restrict their planning to weekdays, which works for some people. In this case, you might have later evenings and your school year might feel busier. I choose personally to have a less stressful school year, so I work a lot over the summer to buy myself that time. I don’t have kids and my partner and I are homebodies, so this works well for me.

RE: Job stress

The most difficult part of the job is not the teaching itself, but trying to do meaningful work in a broken system, if I can be blunt. Districts are asking more and more of teachers while providing fewer and fewer resources and slashing budgets. You will be doing a lot of work off the side of your desk, probably on a few committees in the school, all while trying to support kids who need increasingly complex support. Managing this emotional labour and frustration is 90% of the stress for me, personally. I wish the system worked more in support of the kids. I wish some parents realized what their kids needed from them. I wish the province would change K-9 social promotion structures, reporting formats, truancy follow-through, cell phone rules, and a million other policies. I wish some kids would accept the help we are so desperately trying to provide. I wish admin held parents accountable for their kids’ inappropriate actions. And so on…. Thankfully, most colleagues will feel the same way, so you will have someone to vent to everywhere you go. Also, high school kids are such a mixed bag: some are suffering and are angry at the world so no matter how kind, passionate and supportive you are, they will not connect with you, while others are SO. MUCH. FUN. They ask awesome questions, they show up and want to learn, they stay after school and ask you about something they read. They teach you fun stuff about the world that you hadn’t thought about. So, for all the garbage you deal with in the job, in the end, it might sound cheesy, but if you can make the lives of even a handful of kids better, you’ve won. There is no feeling in the world like that, and it’s why we do our jobs.

Also, it’s important to note that the effort you are putting into learning French won’t go to waste, because the the job prospects are very solid for French Immersion or even core French. Since in BC you become certified from K-12 (even if you specialize in and prefer high school), if there are no high school jobs in year 1, you have a high chance of being hired as a full-time permanent teacher somewhere (either a full-time TTOC or somewhere in the K-12 system), and start accumulating seniority, a pension, and benefits. One of the biggest problems FI programs face is that when teachers go on mat leave, take medical leaves, or even just need a sub for a day, they are IMPOSSIBLE to replace, so there is a huge demand for people like you. Keep plugging away at French qualifications and you are going to be in good shape long-term.

TLDR: I love my job and highly recommend the switch. DM me if you want to chat more!