Is it bad to teach high school science for a few years before attending graduate school? I've just graduated with my BS. I have been offered a job to teach biology at a christian university prep academy. I desperately need the money, and I was raised religiously, so I expect that I will be able to do the job fairly well. However, once I get a stable financial foundation, I want to get a PhD in cell and molecular biology. Will teaching at a Christian high school basically be "career suicide" for me? Will I forget all the complex things I've already learned?
Teaching experience is a good thing.  If you want to teach again after completing your PhD, the teaching experience will help you get a job.

However, I have doubts about your financial strategy.  In most STEM fields, you can expect to get paid more if you have a PhD.  The sooner you complete your PhD, the sooner you get the extra pay, and the more years you will keep the extra pay for.  I am not knowledgeable about teacher pay, but I suspect that the best American PhD programs pay students only slightly less than typical entry level high school teaching jobs in America.