Pupils at Lound Academy in Chapeltown say speeding cars and inconsiderate parking along what is a busy commuter route pose a double threat to their safety.
They have launched a petition, which has already been signed more than 500 times, calling for double yellow lines and a pelican crossing outside the school on Lound Side.
It is backed up by a video, in which the heads of school council Kaiden and Bethany take centre stage.
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"The school is at the top of a hill and on a bend too. This adds an extra risk when trying to cross the road safely," the pair tell viewers.
"It's very difficult to see cars coming especially when people park here."
The petition describes the existing situation as 'an accident waiting to happen', especially with the nearest safe crossings more than a mile apart.
It tells how pedestrians are forced to lean into the road to see past parked cars, and claims several parents and children have already been involved in near misses.
"There have already been collisions outside of the school gates; thankfully these have been minor prangs, but how long before there is a serious accident or fatality on this busy stretch of road?" asks the petition.
"The school has sent several letters to parents, reminding them to park considerately. We are also working with the local PCSOs who have been distributing tickets. Unfortunately the problem persists - much to the annoyance of the vast majority of our parents."
The petition passed the 500-signature mark within three days of being launched.
Lindsay Owen wrote on the petition website: "I have a child at this school and the parking situation is very dangerous and something needs to change!"
Emma Seaton commented: "Parking round schools is getting worse and it's only a matter of time before an innocent child is seriously hurt because of inconsiderate and dangerous parking."
And Amanda Furniss added: "It's a nightmare if you drive past at home time - even creeping along, you are dodging illegally parked cars or double parked cars which are jeopardising children's safety."
You can sign the petition, which will be delivered to Sheffield Council, at change.org.