It would better improve the paragraph because it has nothin to do with the rest of the paragraph. The paragraph seems to be about team sports and promoting it, while sentence 3 is about individual sports are better then team sports. So removing sentence three would better promote CO-ED team sports.
Answer:
Low self-esteem
spending a lot of time alone
Reluctance to let parents or other family members anywhere near their mobiles, laptops etc
Finding excuses to stay away from school or work
Friends disappearing
Losing weight or changing appearance to try and fit in
Fresh marks on the skin that could indicate self-harm and dressing differently such as wearing long sleeved clothes in the summer to hide any marks
A change in personality i.e. anger, depression, crying,
