Scary librarian face??

Today was my first afternoon up the school listening to the children read. It was a bit more difficult than I imagined. Plenty of giggling and whispering and kicking of chairs. Discipline has never been my forte. Do I keep telling them off and try to be scary or do I keep it nice but firm. Have made the grievous error of wanting them to like me although most of them know me from the library or as Ryan's mum anyway.
Apparently it is easier to go in hard and get softer than the other way around. What worries me is that these were only year 4 and 3. Tomorrow they want me to start on year 5 and 6. It is so hard to keep them on course once they start talking about something. This afternoon I found myself in the middle of a bizarre conversation about the merits of beheading over being hung drawn and quartered. Also how effective hanging is. Oh dear I can see a talk coming off the head teacher after all the parent complaints.They also spent 10 mins laughing over Thomas Pooper. I must at least keep the illusion of control.
I have had three cans of coke today. Is this good or bad. I always remember reading about this woman who drank 20 cans a day so I tend to use this as my bench marker, it makes me feel better.