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."
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It's hoped more people will consider using their local service amid concerns over the future of the bus industry.
Dry across the country this evening with broken cloud and some late sunshine. Scattered showers expected tomorrow.
40,000 people are expected at the motorbike event in the capital this weekend.