In a statement on Cwmcarn High School's website, headteacher Jacqui Peplinski said "concerns were dealt with swiftly".
"There was no risk to any staff or learner and the relevant support services were contacted as a precautionary measure."
"Cwmcarn High is a caring and safe environment and we are committed to everyone’s safety."
More top news
Cold weather is again on the way for the UK. Colder conditions will spread south, bringing a mixture of sunny spells and snow showers
Siarad cymraeg McBusted? Well you will be by April! Pop band get a lesson in Welsh ahead of their Cardiff gig
Clear spells across southern and eastern parts will lead to a chilly night with a local frost possible