Over the course of this season, the Crystal Palace Girls Under-12 team have become used to a familiar routine when they turn up at grounds and parks across south London.

Their arrival always causes a hum of activity, an audible chatter amongst players, fans and parents. There will be a few long stares, and often a sharp intake of breath as the opposition come to realise they are about to play a team consisting entirely of girls.

"When they first see us, boys start whispering to their friends and laughing at us because they think we are going to be easy," says Crystal Palace Girls' 12-year-old defender Remmi Gardner. "We see that and think, OK, we will show you."

Palace striker Lily Edwards knows only too well what's at stake: "You can hear their parents saying, 'Oh come on, boys, they’re only girls, you have to win this.'"

These girls are pioneers, making history as the first generation of young female players to compete against boys in their own leagues.

This season, 68 elite girls teams at Under-10 and Under-12 levels—including those from Chelsea, Manchester City, Arsenal, Liverpool and Crystal Palace—have been playing in local grassroots boys leagues.

Before now, it was strictly girls versus girls. But Kay Cossington, the Football Association’s head of women's talent and England’s Under-15 girls coach tells Bleacher Report that last year, the FA made the radical decision to experiment with playing girls against the boys.

"A lot of thought went into this because we wanted to give the most talented girls in the country the best competition experience possible," Cossington says.

"We wanted to stretch these girls, toughen them up and make them better players by throwing them in against the boys, so as to help them become quicker, more creative, and more physical."

Nesta Hibbert has been managing Crystal Palace’s U12 Girls team for four seasons, and she was initially shocked when she heard of the FA's plans. But on reflection, Hibbert, the sister of former Charlton and West Ham defender Chris Powell, thought her girls would relish the new challenge, having grown tired of winning most of their games.

During an earlier season as Under-10s, the Palace Girls were utterly dominant, winning 23 of their 24 games, scoring 135 goals and conceding just four. They had become too good for their fellow girls.

"We were winning games with ease, and after a while that gets boring," says Hibbert, who runs the side along with head coach Dylan Charlery-Bowen.

"We would regularly win by eight or nine goals, so the idea of taking on the boys sounded exciting and the challenge they needed. There was some reluctance, but all came to see we needed to test ourselves. It has been a great wake-up call."

Twelve-year-old Sophie McCormick is the bright and enthusiastic captain of the Crystal Palace Girls. She plays in central midfield.

"I was really excited when I heard we were going into a boys league, because I wanted to prove girls were just as good at football," she says. "We are completely equal. A lot think football is a boys' sport, but we are showing that isn’t the case."

The Palace Girls entered this brave new world with a jolt, suffering a 12-2 defeat in their opening game against a boys team.

"It was a shock to the system," Hibbert says. "After the first three goals, I could see the girls shrink in size and their shoulders sag. They were stunned. They had not lost many before. They weren’t even used to conceding many goals. They could have given up, but they didn't, and they have kept battling all season."

The Palace Girls lost the majority of their early games, and heavily too, going down 7-1, 6-1, 4-1 and 5-1, as they adapted to the new realities of playing boys, whom they found to be faster and stronger.

At the start of the season, their main concern had been the greater physicality of boys and having to tackle them.

"We were worried that the boys would be a lot more rough and could hurt us," Remmi says. "But when we started playing, we realised not to worry and just get stuck in. If they barge us, we give it back to them, and they have been shocked at that."

Sophie shared these concerns, but she too has thoughtfully managed to overcome them during the season.

"Boys are about being physical, whereas girls use their minds; we try to think about the game more,” she says. "We draw them in and pass the ball around them. Girls are more focused on being technical, while the boys are on full blast, with lots of running."

On the day I watched the girls, a Sunday in early March, they never shirked a challenge and matched the boys for strength and stamina all over the pitch.

After six months playing against boys, here was a team that had grown immensely in confidence. The dismissive words of the opposition and their parents were clearly driving them on.

"Boys always expect to win, you can see it in their eyes," Sophie says. "That makes us even more determined. We want to prove that we are not weak, we can be just as good as them."

Sophie's teammate Lily Edwards hears the disparaging words of parents and opposing players and uses it to fuel her fire. "That makes me angry and want to show them," she says. "I don’t take it personally. They are being silly; of course we can be as good as them."

At the beginning of February, the girls proved their point by securing their first win over a boys side when they overcame Junior Bromleians United with a 4-2 win.

The girls celebrated as though they had won a Cup final, revelling in joyous celebration and taking lots of souvenir team pictures in the goal.

"It was a wonderful moment. The girls were ecstatic; they had proven girls could beat boys. It meant so much," recalls Hibbert. "There had been a fear that we might not win a game all season, but we proved that it is possible.

"The boys team were understandably downhearted as they walked off the pitch, and I even heard some parents say, 'Oh gosh, you got beaten by girls!' But their manager was very complimentary and said he wanted some of my girls to join his team!"

At the end of every match, Hibbert and her girls present the best boy on the opposition with "Man of the Match" awards—a medal to hang around their neck and a bag of sweets.

"You can see the same boys who might have been uncertain about playing girls only an hour earlier are now chuffed to have actually earned their respect," Hibbert says. "It is a nice moment."

At the match I attended, played at the girls' home ground at a school in south London, the boys from Caribb FC had to fight all the way for a narrow 3-2 win. Afterwards, they wore sweaty expressions of undisguised admiration for the girls who had just matched them.

"I can’t lie, I thought it would be easy," said Caribb FC player Romel Gambicky. "But it was tough. They were really good. They have some great players."

Six months after sending the girls into the unknown, and with evidence in games like that one, the Football Association are keen to declare the experiment a triumph.

"It has been a huge success. The feedback from coaches, players and parents has been really positive,” Cossington says.

"Over the season, the girls have all developed their games: learned to be quicker and play the ball forward more, as well as how to deal with the strength of boys and use their bodies to protect the ball. Boys start kicking a ball when they can walk. They watch Match of the Day, they play FIFA. It is natural for them, but girls start later, so this season playing against boys has helped them catch up."

The FA hope this will eventually produce more and better female footballers and speed up their development.

"There is already a lot of talent out there, but now that girls are playing against boys, they will also develop the attitude and strength they need to become professional footballers," says Arsenal’s Alex Scott, who has won more than 100 caps for England.

"You will learn nothing beating other girls teams 10-0, but against boys you will learn to be more resilient and improve at a faster rate. I think in 10 years' time we will see that this will have helped create better women players."

Gone are the days when female footballers were treated as a mere novelty and the sport just a hobby for them. Since the launch of the Women’s Super League in 2011, young English girls now know they can become professional footballers.

The WSL plays host to several leading players, including England internationals Scott, Steph Houghton and Toni Duggan, who can each earn an annual salary of up to £65,000.

England’s run to the World Cup semi-finals in 2015 helped create new heroes and generate even more interest in women’s football.

On the global stage, leading women’s players like Alex Morgan and 2015 FIFA World Player of the Year Carli Lloyd, both from the USA, can earn up to $3 million a year and attract a roster of sponsors, including Nike, Coca-Cola and McDonald's.

"The perception of the women’s game has changed so much in the last 10 years," says Scott, who is involved with Premier League Primary Stars, an organisation that hopes to raise participation in the game. "When I was a kid, my mum’s friends would laugh when she told them I wanted to be a footballer when I grew up, but it isn’t frowned upon any more.

"There is now a pathway, and these girls playing now know they can one day become a professional footballer. It is a career they can genuinely aspire to. They don’t have to go to the USA, either. In fact, as you can see with Carli Lloyd, they are now coming here."

At the start of March, the FA sought to tap into the growing interest in women’s football by announcing their aim to double the number of girls and women playing the sport by 2020. The governing body has long wanted football to be a genuinely national sport—not just a boys sport, where girls felt relegated to the fringes.

The FA’s chief executive, Martin Glenn, even declared at the launch, as reported by the Daily Mail, that he firmly expected England’s women to win a World Cup before the men, citing their superior toughness and mental fortitude.

Placing girls in boys leagues this season has been done to aid this process and make them physically and mentally stronger. Some of the girls playing for the 68 elite teams in boys leagues, possibly even from the Crystal Palace Girls Under-12 side, could go on to represent England and win this World Cup

"I would love to be a professional footballer. I have been dreaming about that, and hopefully playing against boys will help me do that," Sophie says. "I have come on a lot playing against them. It has made me tougher, fitter, stronger and faster."

This season’s experiment has even started a debate that it could lead to a woman playing in the Premier League in the future.

"I can definitely see that happening," Hibbert says. "If they are now playing together at this youth level, then why not?"

For now, the Crystal Palace Girls will return to playing in a girls league next season when they graduate to be Under-13s and play 11-a-side football for the first time, but with the new rule that they must also play five extra games against boys teams.

Some girls are keen to return to this safer environment, but most will miss the weekly challenge of taking on the boys.

Their captain, Sophie, speaks for most of her team-mates about this bruising but ultimately rewarding season when she reflects, "Our main goal was to prove girls could be just as good as boys at football, or even better and actually beat them, and I really think we have shown that. We can be really proud of that."

Sam Pilger is a contributing football writer at Bleacher Report. You can follow him on Twitter @sampilger