Parents have been urged to remind their children of the danger of speaking to strangers after an incident near Headlands School yesterday morning.
Full details of what happened have not been made public, but the school has confirmed that police have been made aware and are treating the matter 'very seriously'.
A message was sent to parents after school yesterday, telling them to remind children about what to do to stay safe.
Then, later in the evening an update from headteacher Sarah Bone was posted on the school's Facebook page
In the message, she says: "Humberside Police are investigating an incident that took place today before school started on Sewerby Road.
"They are, rightly so, taking the incident very seriously.
"Their response was swift, precise and thorough. As I am sure you can appreciate we have to act on their advice during any criminal investigation so as to not jeopardise the integrity of their enquires and any potential future criminal conviction.
"The police advised us to remind students and parents of 'stranger danger' protocols so that parents could discuss with their children what to do if they were approached by a stranger or saw someone acting suspiciously in their presence.
The school says that before yesterday's incident came to light, it had already planned to carry out 'lockdown' drills this term, similar to fire alarm practices
"The message is clear - don't talk to any strangers and report anything or anyone acting suspiciously to a responsible adult as soon as you can. This is indeed what our students did this morning before school had started.
"The students involved in the incident went straight to Student Services. Our students, your children, really do understand this message and know my team and I continue to do everything we can to keep them safe.
"Separately, but coincidently, we advised students before Christmas that alongside our termly fire drills, this term we would also be undertaking drill 'lock down' procedures.
"We decided to advise students about this following another successful whole school fire drill. In our experience 'forewarning' the students helps to reduce their anxieties when the drill then takes place and also allows them to ask any questions - for example what to do if they are in the toilet? What do they do if they are out on the sports field doing PE? Questions we have been able to answer before the drill so that panic and confusion doesn't then ensue."