Mills and Robson are both familiar names to Gloucester Rugby supporters having featured regularly at England U18 level last season.
Meanwhile, Koree Britton, who moves from Ivybridge College, has also been a part of the same England U18 squad this season and scored the first try recently as England wrapped up a third successive Grand Slam with victory over Ireland at Llandovery.
The value of the club's ongoing link with Hartpury College is highlighted by the fact that Casson, Evans, Langley, Mills and Robson are all students at the college whilst Hayes is a product of St Peters School.
Greenaway told the club website today that the new recruits will help to continue the progression of talent through the Academy and into the first team squad.
"Gloucester is a club that's proud of its traditions and heritage, none more so than producing homegrown talent."
"We all recognise that it's vitally important that Gloucester develops local players who can compete at the highest level and bring the passions and desire that comes with playing for your local club."
"We've seen the likes of Freddie Burns, Jonny May and Charlie Sharples making a huge impact at first team level so far this season and we've been delighted to have five players in this year's England U20s Six Nations squad with three of them currently in Argentina for the Junior World Cup."
"These young players are the next generation and we hope to see them in a first team shirt at Kingsholm in the not too distant future."