The seven-strong teaching team from Purbrook Junior School will scale down the Spinnaker Tower on July 24.
Money raised will go towards the school minibus to transport children to festivals, events, sports, and museums.
Purbrook Junior Support Association, a group of parents, has been leading the fundraising drive.
Emma Murray, chairperson of the association, said: ‘We set ourselves a mammoth task to raise £12,000 for a minibus - then Covid happened.
‘We held raffles through lockdown and started a 50-50 lottery, which is a monthly lottery where half the funds taken that month are won by one lucky winner and the other half goes toward our minibus fund.
‘We are now well on our way to hitting the massive target.’
So far, £8,000 has been collected for the minibus, which will help improve the educational experiences of the 400 pupils at Purbrook Junior - transporting them to their swimming programme and After School Club trips, among other excursions.
Emma, who will have two children at the school in September, said: ‘At the moment we have to borrow other minibuses to take children to sports competitions and small outings.
‘Children miss out on events because we don’t have the facilities to take them.
‘Having the minibus will open up what the school can offer for the children.’
The head and deputy head of the school will be taking on the challenge, which aims to add £4,000 to the fundraising pot.
Emma said: ‘Some of them will be more nervous than others so we’ll be there cheering them all on.’
With several thousand more pounds needed to hit the target, Emma is appealing to the community for help.
She added: ‘Our children are our future and we need to invest in our future - this will open up so many more opportunities for the school.
‘It’ll provide the minibus for the next four years and hopefully we’ll raise enough money to keep it going.’
The school will also hold a fundraising non-school uniform day.
To donate, visit justgiving.com/crowdfunding/purbrook-pjsa.