Nurseries are being encouraged to practice emergency lockdown drills, in case intruders manage to gain access.
A body representing nurseries has created a plan to help staff practice with children without scaring them.
The chances of such an emergency are extremely rare, but some schools in the west of England have used their lockdown procedures in recent weeks.
Hayley Fitton-Cook, from Snapdragons Nursery in Bath, said they treat it "like a game of hide-and-seek".
In the past two weeks, serious incidents at a school in Tewkesbury and also in Swindon have led to lockdowns.
It is something nursery staff are also practicing following advice from the National Day Nurseries Association (NDNA).
"In a similar way that we do a fire drill, the lockdowns will allow children to move to a place where they can feel calm and quiet, and they sit and wait until they're told it's safe to come out," explained Ms Fitton-Cook, the nursery's safeguarding lead.
