Mark Shipman penned a letter to mums and dads after officers were called out to Springs Academy in Arbourthorne on Friday, May 27.
A South Yorkshire Police spokesperson said officers were called out at about 10.30am to ‘check on a 16-year-old student that had been reported missing.’
They added: “The student was located and became aggressive towards the officers causing minor injury to one police officer. He was arrested on suspicion of assault.”
Mr Shipman said: “You may be aware that uniformed police attended the school today (Friday). This correspondence is to reassure you about your child’s safety and, unfortunately, to address some inaccurate speculation on social media.
"The incident that police were responding to concerned a single student and the issue was not school-related. No other students or members of staff were involved.
"All staff and students were safe and secure at all times and remain so now.”
Mr Shipman added: “To remove any doubt: the school will always communicate with you if there is an incident in school that we believe has a bearing on your child.
"We will always give as much information as possible whilst maintaining confidentiality about detail where necessary. We always seek to protect the dignity of young people in this situation.
"Sometimes speculation on social media makes this much more difficult.
"Thank you to the vast majority of parents and families who trust us with their children on a daily basis.
"Please do contact me personally if you have any further issues regarding this situation.”
This latest incident comes a few months after a previous unrelated incident in which trespassers allegedly brandished knives at the school.
A video was widely shared on social media showing students screaming in terror amid reports of trespassers on school grounds armed with knives.
Officers were called to the school on Hurlfield Road at about 3.15pm on February 2 to reports of two males on the grounds with a knife threatening pupils and a member of staff.
Neither of the males, believed to be teenagers aged between 15 and 20 years old, were pupils at the school.
Police say one one of them was wearing a black coat with the hood up and the other was white with a red coat on and a snood around his face.
The man in the black coat was allegedly carrying a knife.
They had left the school premises by about 3.20pm.
South Yorkshire Police confirmed at the time that three teenagers were arrested in connection with the incident.
Two 16-year-old boys, and another aged 15, were arrested on suspicion of affray.
We have asked South Yorkshire Police about the latest incident on May 27 and are waiting for a response.
Anyone with information about the previous February 2 incident can call police on 101 and quote incident number 585 of 2 February.
Alternatively you can stay completely anonymous by contacting the independent charity Crimestoppers via their website Crimestoppers-uk.org or by calling their UK Contact Centre on 0800 555111.