You asked

How do I encourage a good attitude towards sport in my tween?

There are many benefits a child can gain by playing sport including a healthy mind, body, life skills and friendships. Teaching your child to be a good sport from a young age will mean you will help him get the most out of the game.
Effort equals success
One minute your child is being cheered for scoring the winning goal in a match, the next he can’t believe he missed the goal posts!
The wonderful thing about sport is that your child will get the opportunity to experience emotional highs and lows in a structured environment. It also gives your child the chance to experience being part of a team, how to be a good winner and loser and how to cope with disappointment.
Sport also teaches your child about the importance of trying hard even if it doesn’t always mean winning. For instance, he might do a really great job, kicking the ball but the team might still lose the match. It’s important that he knows he has done his best.
Encouraging a positive sporting attitude
You are your child’s most influential role model and this is certainly true when it comes to sport. When you’re watching sport together, make sure to point out how well the losing team played and try to avoid making negative comments about losing.
Find out what why your child wants to play sports and try not to place any unnecessary pressure on him to do well. When your child comes home after playing sport, ask him if she enjoyed the match before asking if he won. Place an emphasis on enjoyment, participation and effort, rather than winning and losing.
Getting involved in your child’s sporting events shows him how you support his participation. There are many ways for you to get involved, such as washing the netball bibs, working in the club canteen or being the team scorer.
As your child gets older
As your child gets older, sport can become more competitive and there can be a greater focus on winning and performance. This can result in some children being left behind. If you feel your child isn’t enjoying her sport anymore, think about ways to keep her involved, including changing to a new team or trying out a new sport.

More questions

Parents nowadays have such busy lives so it can be hard to ensure that your tween is being active when you feel like collapsing on the couch for the evening.
Everyone knows that exercise is good for our bodies; it’s also good for the brain.
If your child announces he doesn’t want to play sport anymore, it will be helpful to know why he has reached this decision.
There are many benefits a child can gain by playing sport including a healthy mind, body, life skills and friendships.
As we all know, exercise is a central part of weight maintenance and many kids don’t get enough of it. 
The best way to encourage your child to be active is to be active yourself.
Some children don’t have the basic physical skills for some sports. Being unable to master a particular skill or activity can make a child feel like a failure. 
There are lots of popular sports for children to choose from.
If your child wears contact lenses then there are some general guidelines you should ensure they follow while playing sport.