EFC will be decided by your family and kid income (TAX return as proof, get ready 2 years in advance in case your kid apply early decision, one year in advance for regular admission.) and parent's asset and kid's asset.
To make it simple, if your current family income is above 180K, don;t expect much even from a private school, definitely no chance from a public school since the total cost is less. If your income is between 60K--180K, something you could do--mainly reduce your asset ( transfer to retirement accounts, which is not counted) and reduce kid's income and asset. Under 60k annual income, your kid are free to go to college.
Since you have a business, I am not sure how the college calculated on this. The income might be easy to figure by your income tax return. About the asset, I have no idea. For primary resident is is very easy, your house value-mortgage. For asset, you can count 6% as EFC anually.
Hope these 2 old articles helpful for you to understand.
http://blog.sina.com.cn/s/blog_630b4b010100flta.html
http://blog.sina.com.cn/s/blog_630b4b010100fx29.html