Dear mother,
Don't be worried.
I am a student fond of the Internet,too.Like you,my parents are also worried about me.But you know everything has its two sides,because there are a great many advantages of surfing the Internet and a lot of websites serve the purposes of education,so students can make the best of the Internet for learning.For instance,they can ask questions immediately through the Internet and search for information for self-study.
I suggest you should tell your son about your worries directly and make a deal with him instead of forbidding him from using the computer,but tell him to surf the Internet not more than two hours each day after finishing the homework.It is useless blaming him for playing computer but trying to reason him into study.
Yours sincerely ,
Chris Wong