A former lecturer in construction management at Gloucestershire College of Arts and Technology in Cheltenham, he joined the Warriors Academy from Hartpury College in Gloucestershire, where he was director of rugby, in January 2005.
Stanley - affectionately known as Stan around Sixways - has overseen the development of a huge number of young players at Warriors, including the likes of current first team stars Matt Mullan, Chris Pennell, Jake Abbott, Alex Grove, Matt Kvesic, Jonny Arr and Joe Carlisle.
He said: "I have enjoyed my time at Warriors immensely and I have been fortunate to work with some very talented people.
"I was a player at Gloucester for 13 years and started my coaching career at Kingsholm so this is a good chance for me to return to a club where I played all my rugby. It was an opportunity I couldn't turn down and it is the only club I would have left the Warriors for.
"They say if you can leave something and feel it's in a better position than when you found it then you can be satisfied and I certainly feel that is the case at Warriors.
"In terms of coaches, not only have I enjoyed working with the existing crop, headed by Richard Hill, but also many others throughout the club structure. Stuart Pickering, Mike Lancaster, Karl Denvir, Tom Tench and Ben Mcdonald have all come through the Academy as part of the backroom team and made an impression. I am also confident that with the current calibre of talented backroom team of Simon Lane, Ryan Fisher, John Chaffe and Dan Lyne the Academy is in good hands for the future.
"I've clearly enjoyed working closely with Gary Meechan and we've overseen the development of a significant number of players that are currently within the first team squad, including our club captain Chris Pennell and a host of current internationals, some of whom now ply their trades at other clubs. We've been lucky to work with some very good players and have always looked to create an environment where there is a real desire to play for your club and realise how special that is.
"We sat down recently and worked out over 30 players from the Academy have played Premiership rugby either for ourselves during the period we have worked together which is significant. It gives you a huge sense of satisfaction when you see the likes of Matt Mullan and Alex Grove gain full international honours while they have been at the club and even people like Tom Wood and Dylan Hartley making their England debuts.
"I'd also like to pay tribute to Chairman Cecil Duckworth. During my time here he has been fantastic and clearly takes great pleasure in seeing home-grown players come through the system. The opportunity he has given me and support has been excellent.
"Although I am leaving the club I will retain a strong interest in how the Warriors do and look forward to seeing how the players I've worked with continue to develop and improve. I will keep in touch with many of them and wish the club and supporters every success for the future."
Head Coach Richard Hill paid tribute to Stan's outstanding contribution during his time at the Warriors.
"I have known Stan for a long time, since my days coaching at Gloucester when he was a player. I always liked him from the word go because he had a superb attitude, was a grafter and all about 100 per cent commitment," said Hill.
"I coached him for four years and was delighted when I arrived here and our paths crossed again. It was good for me to know him before I came and have that strong relationship.
"Stan puts the same amount of work into the Academy as he did to his rugby when he was a player. He is very serious about his work and very loyal so I understand how hard a decision it would have been for him to leave Warriors.
"The hours he works in the Academy along with Gary (Meechan) have been staggering. It is also testament to them and the way they work that every player who has come through that system has a terrific work ethic and attitude.
"The quality of players produced by the Academy here reflects on coaches who have worked with them so there is no doubt Stan will be missed. But he is well known and well thought of in Gloucester and so we understand the decision he has made. I have huge respect for him.
"We will not be rushed into a replacement," added Hill. "These are big shoes to fill and we will take our time over replacing and get that decision right to ensure we carry on the good work that Stan has been doing."