This story has been updated.
A boil water advisory is in effect at Chester District School.
The school made the announcement on its Facebook and Twitter pages before 10 a.m. on September 18 and said the South Shore Regional School Board (SSRSB) will supply bottled water for drinking.
"The SSRSB is working to correct the problem in close consultation with the Department of Environment and the Medical Health Office. We will notify you when they lift the boil order."
School board communications coordinator Theresa Schroder said bacteria was detected and the school has since shut off all of its water, informed parents, and ordered water from Culligan.
She said the school regularly tests its well water and uses a UV light for treatment.
The advisory is only in effect for Chester District School and not Chester Area Middle School.
The water will be tested again twice tomorrow and Schroder said the advisory will be in effect for about a week to a week-and-a-half so samples can be sent to a lab for further testing.
A spokesperson for Nova Scotia Environment said in an email statement that the boil water order was issued as a precautionary order, which is policy when a water sample shows the presence of total coliform.
Total coliform is a group of bacteria naturally found in the environment and is not likely to cause illness, but its presence indicates a water supply may be vulnerable to contamination from more harmful microorganisms.
The spokesperson said no E. coli was present at Chester District School.
"The order will stay in place until the well is tested again in a few days. The school is in compliance, and is ensuring all students and staff are aware of and respecting the boil order."