To a great degree, this answer to this is subjective; what some people might consider positive, others would consider negative.
One strong positive for many people is the ability to keep in touch with friends and family in distant places. As our society has become more mobile, it has become increasingly difficult to stay in touch with people as we move around. Social media allow for maintenance of social networks irrespective of geographic location.
On the other hand, it can be argued that the sort of connections we make on social media are inherently superficial. Posting or "liking" a photo or a short update isn't the same as meeting someone in person, sharing activities, and having deep, significant conversations. Platforms such as Twitter and Facebook encourage very short and necessarily superficial interactions.
While social media allow us to meet like-minded people from around the globe who share our interests, which is positive, there can also be a "bubble" effect in which we only encounter ideas and people within our current comfort zone.
Social media can become an incredible waste of time and distraction. If not used wisely and responsibly it can have negative consequences. Everything that is posted online becomes part of your digital footprint visible to the world. This should be taken into consideration as potential employers will have access to your digital footprint.
However, Social media can be an amazing tool for collaboration and networking. In the field of education, it has become a great tool for learning and professional development. You can connect with other people in your field in other parts of the world to learn from and collaborate with each other. It is also a great way to get helpful and essential information out the the community, whether it be parents and/or students.