Most schools in Newtown opened on Tuesday, four days after a gunman fatally shot 20 children and six adults at Sandy Hook Elementary School.
But in a letter to parents published by WFSB-TV, the principal says students at Head O'Meadow Elementary School should stay home because police were prepared to have the school in lockdown. School officials said the lockdown was normal procedure because some threats were predicted by police.
All other schools in town, except Sandy Hook, opened on Tuesday.
A police dispatcher would not confirm the lockdown.