Great question! It can be very frustrating when a parent tries to encourage their youth to read more while they are more interested in playing video games or hanging out with their friends.
There are a couple of things you may want to consider before you jump into an action plan to get your child to read more. First, do they have access to a variety of books or reading material? Do you take them to the library and let them explore their own areas of interest? Also, do they have enough time to read? Some children are so inundated with activities and obligations that they don't have much free time to leisure read. Another thing to consider is if your child has a tough time understanding or comprehending what they read. Sometimes kids don't do well in a particular school subject or activity because it's very difficult for them and they are embarrassed and afraid to tell someone about it. You can test this by asking them to read along with you for a few paragraphs.
If they are simply spending too much time on video games, television, or friends, it's up to you to restrict their access to those things.
Spend some time assessing why they may not be interested in reading, but remember that it's also very normal for a 9 year old to be more interested in physical activity such as going out and playing with their friends rather than reading a book.
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This is a very common problem at this age, so don't worry! Here is an article that should help you out, with concrete tips about finding the right kinds of books to appeal to reluctant readers in middle school, plus book suggestions. Good luck!