T-Mobile want to build a 15 metre tall mast near the school on land owned by Hemingby Agricultural Traders on the Reindeer Close Industrial Estate to provide coverage for the town.
QEGS headteacher Tim Peacock said: "It is not appropriate to site a mast next to a school. The risks associated with non-ionizing radiation are very unclear.
"The governing body takes the view it must exercise its duty of care and object very strongly that pupils and staff should not be exposed to unecessary risk."
He said worried parents have written in to complain about the plan.
T-Mobile is holding a drop-in session at the Admiral Rodney in Horncastle on Wednesday July 26 from 4.30-7.30pm for people to find out more.
The company says it has to build a new mast in the town as the current one on land off Southwell Lane has to be taken down - to make way for Chartdale Homes building 70 houses on the site.
T-Mobile say depending on the reaction from people at the drop-in they may then submit a planning application to build the mast to East Lindsey District Council.
A spokesman for T-Mobile told the News the World Health Organisation say there is 'no convincing scientific evidence' mobile phone masts cause 'adverse affects'.
They added all their mobile phone equipment conforms to stringent international guidelines.
Mr Peacock said if a planning application was submitted the governors would 'very likely object'.
He added he was concerned this next phase of consultation was taking place at the start of the school holiday 'when opportunities for objection would be reduced.'
Sue Emmson, who lives off Lincoln Road, is concerned on two counts - she is near the site and her daughter Jessica goes to the school.
She said: "A school is the wrong place to put it. It is the unknown - no one can prove one way or the other about these masts."
But another nearby resident, who did not wish to be named, told the News: "I'm fine with it, it doesn't bother me."
* T-Mobile say concerned parents can contact them for information over the school holiday on 08703 216047 or at networkinfo@t-mobile.co.uk

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