Emergency services remain at the scene at Outwood Academy School on Clotherholme Road in Ripon.
Police were called at around 12.30pm on Wednesday 11 November, to reports that a number of students had collapsed at the school and a number of others had taken ill.
It is believed the incident happened sometime between 11am and 11.30am.
Approximately 27 students have been affected who have displayed signs of sickness and feeling faint. Some have been attended to by paramedics at the scene and two have been taken to hospital.
At this stage it is not known what has caused the students to fall ill and officers are working with the fire service to establish what has caused the incident.