Peter Bumby had just turned thirteen. He was quite tall for his age and well-built. He had short blond hair and blue eyes. This morning he was wearing a clean white shirt tucked in and his navy school tie with yellow stripes was neatly tied. Instead of his usual navy school ones, today he wore a new pair of smart grey flannel trousers, fastened with a black belt. His black shoes were well-polished.
As he was walking to school a girl in his class came up behind him. She was slightly shorter than he was and had long dark hair. Her name was Rachel Pearson. She was wearing a white blouse and a navy skirt.
‘Good morning, Mr Bumby,’ she said. Peter blushed.
‘Good morning, Miss Pearson,’ he replied.
‘You look very smart today,’ she said.
‘Thank you,’ he replied. He hadn’t overcome his uneasiness, knowing that she was looking at him admiringly, as if trying to work out what was different about him.
‘Mr Bumby,’ she said, ‘have you got some new trousers on?’
‘Yes, Miss Pearson,’ Peter replied.
‘They’re lovely,’ Rachel said. ‘I think they suit you.’
‘Thank you,’ said Peter.

Personally it sounds way to formal, except if that is what you are trying to do. Sounds like one of my legal reports on an interview

You posted a variation of this on November 11, 2015. Is there more to this story? Do you have a plan?

https://www.wattpad.com/1185329-the-boy-with-the-new-trousers

Complete version above

https://www.wattpad.com/1185329-the-boy-with-the-new-trousers

Complete version above
Yes, like Fr_Chuck said, it sounds formal but somehow that works. I would love to tweak it a bit to correct a few grammar mistakes (but not the British flavor). Do you hope to get it published?