David Andrews (1965-72) who helped organise the 1972 leavers cohort provides an insight into the experience...
I helped to organize a year-cohort reunion that took place last year in May to celebrate 50 years since leaving Price's School. I'd helped to organize a similar reunion to celebrate 30 years too. I can offer some advice on how to go about locating members of your peer group and holding a reunion.
Use the photographs you have to make a list of names from your year. We had about 120 in our year. I used MS Excel to hold the list because its easier than a regular database to add columns for address details, telephone numbers, e-mail addresses and comments. It's also easier to get an overview and colour coding is useful too.
Enter all the contact details you have already. Ask OPs with whom you are in contact for more addresses and contact details. You should consider the implications of confidentiality pertaining to the information in the Excel database. Some of your cohort may not want their details made public. I erred on the side of greater confidentiality than the law expects.
Get a team of OPs together to help organize the event. Divide up the tasks. Treasurer, venue champion, and probably a couple of people or more to work on finding lost members of your cohort. Finding other OPs from our cohort was the hardest work. Two of us did pretty well and we found the whereabouts of about 90 of us. About 8 had died, some we couldn't trace at all. The Office of National Statistics publishes death statistics - I used it to estimate how many of our year should have died. You might like to do the same.
We found that Ancestry was a good source of finding OPs and social media. Information on births marriages and deaths was helpful so too was Companies' House. I focussed on LinkedIn because many people of my age don't like FaceBook whereas LinkedIn is more related to jobs and work. We discovered that deaths abroad are not recorded in the UK so at least one of our cohort, who had died abroad, we located in obituary columns. When we located an OP I tried to telephone him or e-mail or post a letter or even go and knock on his door when I happened to be near where he lived. I enjoyed talking with them and it helped to encourage OPs to attend.
Tracing and making contact with old friends was probably the most enjoyable part of the whole thing including the reunion itself.
We created some newsletters to build-up expectations for the reunion and we circulated about 6 editions on a monthly basis. People liked them.
We elected not to create a web-site or to create entries in social media to promote the reunion. We chose to do this because our search for OPs was so successful we didn't feel the need to create web-pages and we didn't want to put the event into the public domain.
For the 30 year reunion we went to the Moat house hotel (may have changed its name now) in Titchfield next to the A27. That was perfectly OK. For the 50 year reunion we went to the Lysses House Hotel on the High Street in Fareham. That was almost rather cramped at times, we had about 35 people attending but it felt more intimate. Some of us went for a walk the next day to the site of Price's and then down Park Lane to West Street and back to Lysses House.
A group of OPs from my cohort had been meeting regularly over the years and we continue to do so. I enjoy meeting them and have met some of them since the reunion. A group of us are walking the length of the river Thames in small sections of about 10 miles. We stop and have lunch together.
Be prepared that some OPs of your year will want nothing to do with Price's School and other OPs will be reluctant to attend. However, I am sure a sizeable group will want to attend and have a great time.
I hope this helps! Good luck in organizing your reunion!
-- Best regards
David R Andrews