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Twitter is a social media tool facilitating the quick exchange and compilation of information. It has proven useful in many fields, from celebrity promotion to political overthrow.
It can be used as a teaching tool, and should probably be quite easy to incorporate - being popular for personal use, it is likely that most students are already familiar with Twitter. Transitioning to an educational use shouldn't be a stretch.
I can see it being particularly useful for teaching Social Studies - what better way to follow current events as a group than to collaborate on a Twitter feed, following relevent accounts and hashtags. A classroom could end up with a unique perspective on world events, and analyze the way that their Twitter decisions affected the bias/composition of the news they received.
Twitter is as straightforward as these things come, and I can't see it creating particularly insurmountable barriers for any modern student. In one general way, I think it overcomes a barrier than many modern students may have: Twitter is perfect for the multitasker that we have all become - it provides tiny packets of information, with the option but not the requirement of expanding. It's well suited for the way we now consume media.
Twitter requires its users to be at least 13 years old. So, it won't be a problem for High School classes.
