Armed police were called to South Wolds Academy in Keyworth.
Two boys aged 11 and 14 are reported to have been arrested in the incident.
Nottinghamshire Police were called to the school at 2:30 pm on Tuesday 23rd April.
The school remained in lockdown until approximately 3:30 pm.
Three local primary school were also held in lockdown ‘as a precaution’.
All students are safe – enquiries are ongoing.
The school messaged parents:
“Due to a police situation in the village we have been asked to hold students in school until 3.30pm. All children in school are safe.”
‘“The police have now informed us that students can leave the school and are now leaving the site. Thank you for your patience and understanding.”