Right, I wikipedia'd Sherlock Holmes. Turns out ACD didn't say much about Holmes's early years. Mwu-ha-ha, artistic freedom!
Enjoy!
The circumstances in which Sherlock Holmes was enrolled at the school were shrouded in mystery. In truth, he had simply strolled through the doors, placed £62,000 on the desk and said, "Send a bill to Dorm 8 when that runs out." But to the pupils and the majority of the staff, he had just...arrived. Walked into class with the other boys. Stood in the canteen queue. Naturally, he had no friends at the school. Everyone was aware of Mycroft, the brilliant cricketer and Head Boy, but he left long before the money 'ran out'. And of course, Dorm 8 was haunted, and empty.
That was a given.
It was a Winter morning. The snow fell, Sherlock observed, like in a snow globe. Far too heavy for it to look real. He consulted The Times, which (of course) had been hastily slipped under his door that morning. He flicked through the pages until he reached the small box of a weather report. A snowflake symbol obscured Surrey. "Yes," murmured Sherlock, "Just as one could suspect."
St. Benjamin's School for Boys was tucked into Surrey quite comfortably. Nothing ever touched it. It certainly wasn't Eton, but it had spawned a good many doctors and the like. Which was why, in many ways, it was remarkable for Sherlock to go there. Mycroft had assured his friends that his brother was autistic, and that he would go to a special school. But no, this small specimen of a Holmes sent himself to St. Benjamin's.
St. Benjamin's had broken up for the Christmas holidays- only orphans remained. No-one knew if Sherlock was an orphan. Mycroft had mentioned anything about his parents. Sherlock never mentioned anything. Sherlock today was allowed to wear his own clothes (he wore a cotton shirt and flannel trousers) and do what he pleased. He decided to stay in his room and read the book he had taken out from the library.
Just then, however, he looked up sharply. It was a noise nearly indistinguishable from the usual noises of a quiet school. But Sherlock immediately identified it. "Smart car," he murmured to himself, getting up from his bed, "V6- no, V8 engine...rear wheel drive. Going at 20 miles an hour. Child in the back. New boy."