I'm wondering if any teachers could advise me here, as I'm clueless with regards to Instagram and don't understand how it works 
DD2(10) tells me tonight that a class mate of hers follows her teacher on Instagram and "finds out stuff" (she mentioned his name - no biggie to adults but I guess a big deal to kids who think teachers first names are Mr or Miss)
DD saw me raise my eyebrows at this so she quickly followed it with "oh it's ok, he (teacher is male) knows she follows him and is ok with it".
Now, I really don't understand Instagram at all - is it like twitter where anyone can follow anyone?
And secondly, the teacher concerned is really lovely, and while being an NQT last year had a very steep introduction into safeguarding relating to my DD (not school related) so a part of me wants to just briefly mention it to him - not in an accusing way as I think this is just kids talking. Would teachers want to know something like this, or am I just going to be accused of gossiping?!