we have registers going at the beginnning and end of each session. As the children take off their shoes and line them up we know how many are in/out, however i do not continually check. My garden is secure i know which children i need to keep a close eye on and they free flow without difficulty. We have staff inside and out so i don't feel we need to keep checking...our Lea advisor at one time suggested the children could go in the garden on their own ...i hasten to add that they don't!!! we have walkie talkies to use if needed and we try to stick to a reasonable amount of children in each persons care but i don't overly supervise this. However this works for our setting, the children we have and the layout. You would need to ensure your systems are safe and secure for your setting.