School children in Rhondda Cynon Taf faced a difficult journey to school due to a shortage of bus drivers amid "Covid pressures".
Bus staff are having to self isolate, causing "severe difficulties" in providing a transport service for pupils, Rhondda Cynon Taf council has said.
It put out a statement on Tuesday night, warning of the disruption expected for the follow morning.
"Due to drivers and passenger assistants having to self-isolate, severe difficulties are being experienced in running school transport as scheduled.
"Every endeavour will be taken to minimise delays for learners in the morning.
"However, if their bus does not turn up on time, learners are advised to wait at the stop and a bus will be diverted to cover their service as quickly as possible."
RCT Council leader, Councillor Andrew Morgan, warned: "Covid is still putting a huge pressure on council services, in this case home to school transport."
Pupils attending Cardinal Newman Catholic School and Treorchy Comprehensive School are among those sharing the warning to parents and pupils of delays.