What is the prescribed wieght (in kg) you should be at the age of 13?

Answer 1

Weight is not based on age but on height. Please go to the site listed below, click on the appropriate link (children and teens), enter the required information and it will tell exactly where you stand:
http://www.cdc.gov/nccdphp/dnpa/bmi/index.htm

Since this is in pounds and inches, if you can't figure it out, please email me with your all the information required by the website and I will do all the conversions and post the info here or email it back...your choice.