Halfway through the school year, Maria* became aware that her daughter Sam* wasn't being invited to her friends' houses any more.
"She doesn't always tell me what's going on at school, but I noticed that she was biting her fingernails a lot and sleeping badly. She seemed quite upset.
"I talked to her about her friends and why they weren't meeting up. Eventually, she told me that they didn't get on any more. I found out that her old friends were excluding her.
"For example, when she bumped into them on the street, one of the girls said directly to her, 'This is the one we're not talking to any more'.
"They were also really nasty in the playground. They left her standing on her own. She was still trying to be friends with them, but they just ignored her. She was very upset."
"Then I witnessed an incident one Saturday afternoon. Two of her old friends phoned her. They asked her if she'd started her periods. She said it was none of their business, but they kept her on the phone. She wasn't strong enough to end the conversation.
"They were laughing and shouting, 'We want to know, we want to know'. I was standing next to her, and felt disgusted. I felt really sorry for Sam. Afterwards, I thought of calling one of the girls' mums, but I decided not to because I thought it might make things worse.
"I was very upset because I used to spend a lot of time with these girls, but now they didn't think my daughter was good enough for them.
"I was worried about Sam because I thought it must be horrible to believe you've got really good friends and then they suddenly turn against you."
How Sam got help with bullying
"I told Sam that she should talk to Nicole, a learning mentor at her school. I knew that Sam liked Nicole, whose role was to sort out this kind of issue.
"Soon after, Nicole contacted me. Both she and Sam's form teacher had noticed that Sam was being bullied.
"I found out that she wasn't only being bullied by this group. Sam is half-Polish, and another girl was calling her a 'Polish sket' in class.
"The school intervened quickly. They cracked down on the racist comments and the use of the insult 'sket'. After that, the problem with that particular girl was completely resolved.
"Nicole, the learning mentor, also set up a friendship group to understand the dynamic in this circle of girls who'd all moved up from primary school together. She asked the bullies and a few other pupils to talk together about friendship, boyfriends, fashion, puberty and growing up. A lot was revealed.
"It seems that Sam's primary school friends got to know other girls at secondary school and became more interested in fashion, make-up and boyfriends. Because Sam was more childlike, they didn't want her in their group any more. She wasn't cool enough.
"Sam was different. I think that's often what bullying is based on. She has her own style and doesn't follow everyone else.
"Nicole had several chats with Sam, and helped to strengthen Sam's self-esteem. When she was picked on, Sam used to get quite upset and would try to defend herself, but now she's able to ignore it.
"When I spoke to Sam about the meetings with Nicole, I could see that things were improving. At home, I explained to her that friendships change, and primary school friends don't necessarily stay friends for life. I didn't want to suggest that Sam was the victim because that can make you feel weaker.
"Sam has finally found a new set of friends and is really happy with them. She's become more confident, and she no longer tries to be friends with girls who don't want to be friends with her."
*The names in this article have been changed.
Bullying: information and support for parents
To find out more about how you can help your child if they've been bullied, read Bullying: advice for parents.