Is whole milk good for children between 11-13 years old?

No. American heart association guidelines recommend low fat or no fat dairy products for children 2 years and older.
Yes. While with the rise of childhood obesity and vascular diseases being the leading cause of death, it's been recommended that starting at age 3, children may be switched from whole to 2% milk to prevent hypercholesterolemia. Though, it may have some degree of credibility, i highly doubt that the amount of whole milk ingested by 11 to 13 year old children, will be significant. Whole milk is o/w safe.