LETTERS about truanting will be sent to parents after students objected to the calling off of a sports day at Salendine Nook High School.
Around 20 students are understood to have left the school in protest.
The event will now go ahead next Wednesday.
Headteacher Christine Spencer said the sports day was postponed because the ground was too wet.
She said a lot of children “misunderstood” and went out on to the field, but returned when asked to do so by staff.
A small number, who had not brought their books, decided they did not want to attend lessons for the rest of the day.
Mrs Spencer said letters would be sent to around 20 parents regarding their child’s truanting that afternoon.
She said the Olympic-themed sports day would go ahead and the proposed Unison strike should not affect it.