Rolling out the programme in Hertfordshire will cost an average of £67,000 a weekday during each school break.
The warning from a schools liaison officer came in the week that four Birchwood students tested positive for Covid-19.
"When a member of staff has to self-isolate, that staff member is paid and the school also has to pay another person to teach the class."
The district council's development management committee approved the scheme for The Bishop's Stortford High School despite fierce objections.
How you can get a copy of our photo supplement featuring 34 classes from 24 schools in the Bishop's Stortford area.
Bishop's Stortford High School development will follow construction of new secondary off Whittington Way which is set for completion in 2022.
Claire Stafford, a Year 2 teacher at the Bishop's Stortford primary school, organised a fundraising day in aid of Cancer Research UK.
In Bishop's Stortford, new school Avanti Meadows will give parents and carers a choice of 12 primaries from which to choose.
The 1,011 students at the Stortford secondary have been told not to return before Tuesday November 10 and lessons will revert to online.
St Mary's science teacher shares her story after researchers discovered check by her GP can predict ovarian cancer better than previously thought.
The Sawbridgeworth secondary held Mental Health Awareness Week to "help to normalise mental health and the feelings that often come with it".
In a series of virtual assemblies, pupils learned from different year groups and showcased their creative work.