By Holly Yan and AJ Willingham, CNN

(CNN) -- The Boy Scouts will soon include girls, and not everyone's happy about it.

The 107-year-old organization announced Wednesday that younger girls will be allowed to join Cub Scouts and that older girls will be eligible to earn the prestigious rank of Eagle Scout.

"The historic decision comes after years of receiving requests from families and girls," Boy Scouts of America said in a statement. The group said it considered input from current members and leaders before making the decision.

BSA said the expansion is also aimed at helping busy families consolidate programs for their children.

"Families today are busier and more diverse than ever. Most are dual-earners and there are more single-parent households than ever before, making convenient programs that serve the whole family more appealing," the BSA statement said.

The announcement drew praise from scouting leaders, mixed reactions from women's groups and indirect criticism from Girl Scouts USA.

Friction with Girl Scouts

For months, Girl Scouts USA had a notion BSA would try to start recruiting girls. In August, Buzzfeed News obtained a strongly worded letter in which GSUSA President Kathy Hopinkah Hannan accused the BSA of courting girls to boost falling enrollment numbers.

It's also no secret that BSA membership has been declining for years. In 2016, the organization reported 2.3 million youth members, a decrease from 2.8 million in 2012. The Boy Scouts' membership peaked in 1972, with 6.5 million members.

On Wednesday, Girl Scouts responded to the BSA's announcement without explicitly naming the Boy Scouts.

"The need for female leadership has never been clearer or more urgent than it is today -- and only Girl Scouts has the expertise to give girls and young women the tools they need for success," Girl Scouts USA said.

"The benefit of the single-gender environment has been well-documented by educators, scholars, other girl- and youth-serving organizations, and Girl Scouts and their families. Girl Scouts offers a one-of-a-kind experience for girls with a program tailored specifically to their unique developmental needs."

'The future is bright'

But scouting leaders lauded the expansion, which will begin in 2018.

Zach Wahls, co-founder of the nonprofit Scouts for Equality, said the development was "yet another step forward," for the Boy Scouts.

"Today, the Boy Scouts have made clear they have heard the millions of girls and their families and will allow Scouts of all genders to participate as full members and earn the rank of Eagle," Wahls, an Eagle Scout, said in a statement Wednesday.

"We are proud of the Boy Scouts of America for taking this step forward, and we believe the future is bright for Scouting in America."

Ahmad Alhendawi, the Secretary-General and CEO of World Scouting, tweeted: " "I welcome @boyscouts decision to integrate girls in their programs. On #DayOfTheGirl, we affirm #Scouting commitment to girls empowerment."

The National Organization for Women had a mixed response to the Boy Scouts' announcement.

"I think it's a good thing in that the Boy Scouts have a long history of discrimination and they are taking action," NOW President Toni Van Pelt said. "The devil is in the details and we need to wait and see how this plays out."

The news also received mixed reactions on social media, with some critics calling the move unnecessary and "PC."

Donald Trump Jr. also weighed in, saying, "Strange, I thought that's what the Girl Scouts was for???."

The National Catholic Committee on Scouting, whose stated mission is to ensure the Boy Scouts "as a viable form of youth ministry with the Catholic youth of our nation," said it has accepted the BSA's decision but did not offer a formal opinion.

"Once we have had more time to review the policy and a chance to consult our national membership, we will be able to comment further about how this new policy will reflect changes in the makeup of Catholic chartered units in the Boy Scouts of America," the committee said in a statement.

A new prestigious goal for girls

The decision to allow girls to achieve the rank of Eagle Scout is significant for several reasons.

The rank of Eagle Scout is a prestigious and widely recognized achievement, one that can have long-term benefits in academic, professional and even military spheres. Attorney General Jeff Sessions, Neil Armstrong and Former US Secretary of Defense Robert Gates are just a few notable men who have attained the rank of Eagle Scout.

While there is a rough equivalent in the Girl Scouts -- the Gold Award -- the honor is not nearly as well-known as the Eagle Scout distinction.

The Boy Scouts' announcement fell on the International Day of the Girl, designated by the United Nations in 2012 as a day to discuss and celebrate equal opportunities for young women around the globe.