Bus Éireann says just 20% of its secondary school bus services are operating at the recommended 50% capacity as pupils go back to school.
The operator, which carries out the School Transport Scheme on behalf of the Department of Education, says it is currently reviewing all 2,100 post primary routes it operates to try and meet the new requirements.
But it is understood it could take up to three months before all of the routes which service secondary schools can operate at 50% capacity.
Bus Éireann has begun a recruitment campaign for additional buses and taxis to try increase the number of vehicles on these routes so they can meet the Covid-19 guidelines for school transport.