THE bomb squad were at Greenhill School, Tenby, last week destroying out-of-date science lab chemicals following a national review.
A Pembrokeshire County Council spokesman said that in October national guidance was released advising all schools to check whether their science laboratories were storing the out-of-date chemical known as 2,4-DNPH.
The chemical 2,4-dinitrophenylhydrazine, which is used in A-level chemistry lessons and if it is allowed to dry out it can become dangerous.
The guidance was issued by the government advisory science service CLEAPSS (Consortium of Local Education Authorities for the Provision of Science Services).
The spokesman added: "An amount of 2,4-DNPH was disposed of in a controlled explosion by the bomb disposal team at the time at Greenhill School. A similar process was undertaken at hundreds of other schools across the UK.
"Following this, the school contracted specialists to undertake a complete review of the chemicals stored at the school site. As part of this process, two further small amounts of 2,4-DNPH were located in a secure chemical storage container. They were disposed of in a controlled explosion by a bomb disposal team last week."
Students are still currently on their Easter holidays so no evacuation was required.
At least seven schools in England and Swansea University carried out similar controlled explosions to destroy 2,4-DNPH late last year.