Seven graves in Ferndale Cemetery were deliberately toppled in January and rubbish left strewn across the site.
More than 20 children from nearby Ferndale Community School took part in the litter pick on Tuesday.
A local stonemason has agreed to repair the headstones and South Wales Police is still investigating.
The children collected more 20 bags of rubbish including a broken bicycle and several traffic cones.
PC Steve Davies said he noticed the rubbish when he was examining the area.
"I have a little son who passed away. I know the price, I know the cost implications and the emotional impact it would have on someone to come and visit a grave and seeing that their headstone has been damaged or destroyed," he told the BBC.
"It's just getting people together in response to what's happened to the headstones to build the respect up amongst the community and let them know that we will work together as a team and that people like that won't destroy the image of Ferndale and Maerdy."
Among the pupils helping was Rachel, 14, who said she found the experience upsetting.
"My ancestors' gravestones haven't been damaged and I'm quite grateful but when I see the others, it makes me wonder how their relatives must feel," she said.
"It's upsetting, it's left me quite distraught to be honest."
School pupils have carried out a major clear-up at a cemetery in Rhondda Cynon Taff targeted by vandals.