CBBC Newsround Online looks at how safe schools really are.
Although you may not realise it, your school is probably one of the safest places to be.
Changes were made after the Dunblane tragedy in 1995, when a man broke into a primary school and shot dead 16 children and a teacher.
Since then, schools have been given special money by the government, which they can only spend on making their buildings safer.
These are some of the things you might see:
Annette Croft, headteacher of the Heart of England school in Coventry, told us there had been "huge" changes over the past few years.
- Walkie talkies so teachers can keep in touch with each other.
- Fewer entrances to the school. Most schools only have one way in - often with full-time student receptionists.
- Identity cards for pupils and teachers and special passes for visitors.
- Swipe cards to get in and out of the building.
- CCTV cameras to check on playgrounds and corridors.
- Higher fences and walls, often with barbed wire on top.
"With so many trusted adults around," she said, "this is the one place where you can feel safe."
If you ever feel uncomfortable at school, then talk to a teacher and find out what security your school has got.