At the retreat, the sixth formers will be set team tasks and encouraged to make eye contact, read facial expressions and play board games.
During a chat with pupils, Mr Blond asked one girl which city her friend lived in and was surprised when she did not know even though they had been friends for more than a year.
He said teenagers can sit next to each other every day yet still feel lonely in the bubble of their online world. He told the Sunday Times: "Teenagers can seem so connected but at the same time rather isolated."
Gemma Hannan, who is the director of sixth form, said the idea of a retreat came after teachers noticed the girls' friendships were mostly conducted online. She said: "We find them WhatsApping each other even when they are in the same class. They feel more comfy contacting each other via WhatsApp than talking face to face."
Pupil Ellie Flavin, 17, said many of those she interacts with online are not friends in real life. She added: "Even when we walk with a friend down a corridor, they have their phones out.
"Social media offers virtual friendships. I will see them on Instagram and follow them, but I have never had a face-to-face chat with them."
Florence Andrews, 16, said: "I don't feel I can ask my friends about their families. The friendship is limited to online. It would be weird. There's something caused by social media that makes it really difficult to approach them. It's almost as though we are hiding behind these screens."
Mr Blond added: "The time away is not just for eye contact and board games - but to develop critical thinking, discussion and debate, without the distraction of technology."