Alternative coach operators have been drafted in by Cornwall Council after one firm was unable to fulfil its school bus contract.
The changes affect pupils attending Liskeard School and Community College and Callington Community College.
The existing timetable and pick-up locations used by Darley Ford coaches will be covered by Smiths Coaches, Group Travel and CJ Down Coaches.
No-one from Darley Ford has been available to comment.
Cornwall Council said it wanted to reassure parents and pupils the school service would be covered on Monday.
Smith's Coaches will transport children from the Crows Nest, Darite, and St Cleer areas to Liskeard.
Pupils from the Upton Cross and Tremar areas will be picked up by Group Travel and the service which takes pupils from the Upton Cross area to Callington, will be covered from C J Down Coaches.