The 16-year-old was too young to be given a professional contract so has been able to leave without the Reds being eligible for any compensation.
Manager Steve Evans blasted the rules that meant Crawley would get nothing for the time and effort they have spent developing the player.
He said: "I think it is a shocking rule as if we were a fellow League Two he'd be covered as an academy player.
"I think they have come in for him as I have said a few complimentary things about him in the press and as a club we have a reputation for bringing through really good young players.
"I think he has made the wrong decision, I think it is a backward step but we'll wish him well and see how well he does for them."
Defender Max Lake-Edwards has also left the club after winning a place to study at Oxford University next year.
"He is a really intelligent lad," added Evans. "He'll be moving into their halls of residence in the autumn so he has gone off to try and save some money.
"He took a year out last year to play football but it got to the point where he had to make a decision about where his future lies.
"Young Tommy Brewer has been promoted in his place."