The friends have spent the past two years on their search.
After 60 years, inevitably they discovered some classmates had died, and also not everyone wanted to meet up again, but Karen said the overall response had been positive.
“We had two or three people who are not interested, which is fine it’s not everybody’s thing, but all the rest have responded really well,” she said.
“I’ve got lovely memories, it was a really nice school.
“There was about 90 in the school year and we have tracked down 40 people across England, Scotland, Wales and Ireland and America.”
Some of the group have already met up and 30 people confirmed for the big reunion party this weekend.
Karen said there was a unique bond between the classmates who had known each other before being defined by their adult lives.
“It doesn’t matter whether you’re a cleaner or whether you’re a managing director of a company, we all get on,” she said.
She urged anyone who had started at Rivington & Blackrod Grammar School and was interested in future reunion events to get in touch.