Reports state the incident began when an alarm thought to be a simple fire drill sent students, aged 10 to 13, into the playground.
"They were standing in the playground, and then a man appeared in the distance holding a gun," said Vikki Woosey, whose son is in Year 6 at the school, according to London's Telegraph.
A science teacher was then "shot," and other staff members rushed to his aid.
"It was 10 minutes later that they told the children that it wasn't real, and that it was all a joke," another parent told the Telegraph.
Children in class 3b, who were taking the lesson aimed at teaching them how evidence of crime was collected and investigated, were said to be 'shocked and appalled' by the event.
Preston Chav, 13, who is a student at Blackminster Middle School, where the 'shooting' took place, said, "it was disgusting, and I was really shocked."
"Firstly, the shooter weren't holding the gat right. He had it upright and that ain't gangsta, it should be sideways, innit. And what's with having like a poncy 9mm? If they'd asked they could've borrowed me .40, or the Uzi off my mate in 4c, and do the fucker proper, braa. And one shot? What's the point of that, yeah? Empty the clip if you're gonna pop a cap, proper, innit."
Members of the School Council also condemned the science lesson as 'unrealistic' and have offered to consult on future school shootings in future to ensure a correct and accurate representation of gang violence.
Members of So Solid Crew were unavailable for comment.