In school, I broke something by accident while walking, but they did not call me to fix it or anything. It was not something expensive, but do I have to go back and tell them? They could have easily called me in to fix it, so I do not know what to do.

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.

You are obliged to inform the owners of the thing that you broke, and if they forgive you, then there is no harm on you.

If they oblige you to guarantee it (to pay for fixing it or to replace it), then you have to do so and repair what you have damaged, even if you broke it by mistake.

The mistake does not render you sinful, but it does not exempt you from the guarantee either.

Ibn ‘Abd Al-Barr said in At-Tamheed, “The scholars agreed in a consensus that the saying of the Prophet : ‘Allah has forgiven my nation for things they forget or do by mistake...’ is not about exempting them when they do damage to wealth, but what is meant is that they are not sinful for it.”

The fact that the owners did not contact you does not exempt you from the guarantee and does not exempt you from their right upon you.

Allah knows best.