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
Six companies have announced jobs in the financial and manufacturing sectors, on the eve of the UK Investment Summit.
There will be plenty of cloud and fog around overnight. It looks dull at first on Friday morning, before rain returns across much of Wales.
Tooth extractions among 5 to 9-year-olds increased last year, according to figures obtained by ITV Cymru Wales.