Is this Teacher bullying his student or is it more likely banter?

I was sitting in cl to observe, but I was disguised as a teaching istant. I was placed in a history lesson, with a male teacher who works at an all girls school, the girls are from 11/12 up to 16. He was teaching a lesson full of 14-15 y/olds. He seems to pay all his attention to one girl, lets call her Anna. He's constantly telling her off, literally all I heard through the lesson was "Anna!". She wasn't really doing much at all. EVERYONE and I mean EVERYONE in the cl was chatting and he just picked on her. She forgot a text book, I observed that around half of the cl were missing their textbooks and simply sharing with their partner. But he shouted at her, and threatened to send her out the cl, she simply said "fine" got her stuff together, then he said no forget it sit down. Like he wanted a reaction of her, but why? He admitted to talking about her with other members of staff. Also he embarres her, if she answers a question he'll be like oh well done Anna, round of applause!" In a patronizing tone like he's trying to make her feel inadequate. He's constantly going to check on her, when she's ahead of the people next to her he'll still say, hurry up anna you're being so slow. I remember her saying "Sir everyone else has only done this much". He replied fairly quietly. "I'm not interested in anyone else". Which was odd. Should I speak to a member of higher authority and tell them I've noticed favoritism or disliking, or am I over thinking? It also worries me that this seems flirtatious, kind of like treat em mean to keep em keen, he always tell's her off with a smug look on his face and the "I'm not interested in anyone else" comment could be interpreted differently. Which reminds me there is also another student who begs for attention in anyway, always being loud and chatting, always answering questions and asking him questions, but he's uninterested in her.