How do you manage both parents speaking only one language at home but teaching the child English for reading/writing?

I live in the USA. I've read that the best way for your child to become bilingual is if both parents speak the language exclusively at home. My husband and I can do that with Mandarin. However, how do you also then teach the child English beyond what they learn from interactions outside? I mean things like reading, writing, and good grammar etc.

I know people keep saying they will learn all these things outside the home, but realistically, many Americans can speak, read, and write English, and it is to a pretty good level, but it doesn't mean they do all of these well, so where does the teaching English at home come in if I'm supposed to speak to them in Mandarin only?

What if only one of us speaks Mandarin exclusively to our child, and the other only English? Or does it still work out better for both English and Mandarin to have both speak Mandarin?