My daughter fell off a slide when she was 4, and was in hospital with concussion for a week. The slide was only a metre high but she fell onto concrete, and her behaviour set the alarm bells ringing straight away to tell me it wasn't the usual minor bump to the head. There was the usual crying, but she started vomiting, and was drowsy very soon after the fall. I called 999 and fortunately after a scan and monitoring for a week she was fine.
I cover Head Injuries in the Baby and Child First Aid course, but here's some red flag warning signs of a more serious head injury, when you should be thinking about calling an ambulance...
•No memory of what happended
•Weakness in arms/legs