Really, there's no such thing as 'girl sports' and 'boy sports'. Anyone can and should be allowed to play anything they want, regardless of gender. Human society has become so categorized, so based upon meaningless words we have assigned to people so that there is less competition and a select group of people can pretend they win everything, that some people won't even try something thinking it is not for their 'category'. So anyone should be able to do anything they want.
I have never known a guy that I have played sports against to not go "all-out" against me. Besides recall that whole ordeal with Justine Blainey. She went to the supreme court to make sure that girls could play "boy's sports" (which, by the way, don't exist) She wasn't enjoying girls hockey, so she headed up to a boys team and was one of the most skilled players on the team. Stupid Ideas such as the "girls aren't built to be as strong" kept her from playing in actual games. Similar to what Blainey said, It's discrimination to not let me play on the boys team simply because there is a stereotype that women are weaker than men. Besides not all sports require upper-body strength. Very few do actually. Lastly, Injuries are related to your PERSONAL condition. Bone strength is a matter of your calcium intake not your biological sex. Plus, girls don't have a certain area that is sensitive to pain. Guys do. In that way, we are less prone to injuries.
I think girls should be able to play with boys because one there is no suck thing as a boy sports or a girl sports. Secondly girls are just capable of playing with the boys. Third reason girls are really good at playing sports to why do we look down on girls they are human to we all are equal to each other so stop looking down on them. It is time to stop with that's a boy sport and that's a girls because THERE IS NO SUCH THING OF A BOY SPORT AND GIRL SPORT. Lastly girls can kick boys butt in a sport so anytime any where. And girls can play in football too not only boys are strong and tough but girls are too.
I assume you mean play WITH boys, otherwise it's a non-issue as any sport boys play, so can girls.
There are physical differences between boys and girls that can't be overlooked. At peak fitness, men will always be superior in upper body strength. It's just the ways human bodies are designed. This puts girls at a disadvantage and increases their risk of injury.
Even if you have a few exceptional girls who are physically capable, you have added social stigma against hitting or being aggressive against girls. Not many boys will want to go "all out" against a female opponent if the sport involves physical contact. This does NOT mean there aren't sports that both boys and girls can play together, it just means there will be a few sports that should remain separate.
What do you mean "boy sport"? Please give an example of a sport that girls are not allowed to play. Because I will be very surprised if you can come up with a sport that boys play that girls are not allowed to play. And don't say football, because girls can play football.