Average weight for 8 year old?

You can look on a body mass index (BMI chart) for boys and girls age 2-20. Here is a link that will allow you to find the child's BMI and look it up on a BMI chart to see if the child is Underweight, Normal, At risk for overweight, or overweight:

Boys: http://www.texaschildrenspediatrics.org/healthlibrary/pa_bmiboy_art.aspx

Girls: http://www.texaschildrenspediatrics.org/healthlibrary/pa_bmigirl_art.aspx

Hope this helps!