Parents have complained that confusion over a new school bus service in the county of Conwy meant a number of children had to walk to school.
Llandudno Junction pupils had to walk over the bridge to Conwy
One mother said she was disgusted when she found her 15-year-old daughter had walked along a busy road on Monday.
The council said there had been "teething troubles," but was confident they would be sorted out by Tuesday.
Last week parents met to protest at plans to make them pay up-front for a school bus pass from now on.
Joanna Liepins, who has two daughters at Ysgol John Bright in Llandudno, Leanne, 15, and Jessica, 14, said she found by chance that Leanne had walked to school from Deganwy - a distance of about two-and-a-half miles (4 km).
"Jessica had a lift and I thought Leanne had caught the bus and was safely in school, until I happened to drive past and found her walking with a gang of other children along the road," said Mrs Liepins.
"I was absolutely disgusted. The safety of the children is of foremost importance and it's a long way to walk to school along an open road," she added.
A council spokeswoman said buses had been available, but at a slightly different time.
Another mother said she did not normally allow her 12-year-old son to walk from Deganwy to Llandudno because she considered the route to be too dangerous.
"I found it quite scary that I thought he was in school, but he was still walking there," she said.
Pupils from Llandudno Junction travelling to Ysgol Aberconwy in Conwy were also affected.
"There was some confusion this morning because of the bus timings, and it resulted in a few children being a little late," said Ysgol Aberconwy headmaster David Wylde.
A council spokeswoman said: "There were a couple of teething problems this morning, understandable given that it was the first day back after the half-term holiday".
She said pupils from Ysgol John Bright in Deganwy found one Arriva bus full. Others had been available on different routes, and the council was working with Arriva to remedy it.
"All the Ysgol Aberconwy buses did run as scheduled and we had staff out in Llandudno Junction to make sure all pupils were aware that the bus times had changed," she added.
Both schools are within the three-mile limit and so the council is not legally obliged to supply a school bus.
Parents met last week to object to council plans to make it compulsory to buy a school bus pass up-front or risk losing the service altogether.