How do I go about creating an assessment for a child who has never had schooling?

I am preparing to tutor a friends kid who wants to be enrolled in school. She is 14 years old had has never had any schooling or even homeschooling. Does anyone have an idea on how I should begin creating an assessment to figure out where she's at?

I plan to search through common core standards to find what needs to be met for 8th grade but I'm still not positive of the most appropriate way to go about this without stressing out the child.

I agree with you that trying to meet 8th grade standards with a child that hasn't attended school is not the appropriate approach. She will have to crawl before she's able to walk. If you can get her excited with learning, she will likely surprise everybody with her progress but it works like stair steps that have to be negotiated one at a time. Ask the local school system for advice on what benchmarks she has to meet.

When she is ready, the Khan Academy has many online resources presented as short "how-to" videos if she has access to a computer. They go all of the way from basic levels to the most complicated areas of a number of subjects. Take some time and look at all of the subjects that are available on the Khan web site. It is a great resource for someone trying to catch up. It's free and there are tools for measuring progress.

Example:

https://www.khanacademy.org/math/arithmetic/addition-subtraction/basic_addition/v/basic-addition