Big businesses rarely take courageous stands on hot-button issues that could impact profits. That is why it is worth noting the changes implemented by several Fortune 500 companies following the school shooting in Parkland, Fla., that killed 17 people and injured 17 others.

Citigroup, the giant Wall Street bank, said it would no longer do business with companies that sell bump stocks and high-capacity magazines or sell guns to anyone under 21. Dick's Sporting Goods said it would no longer sell assault-style weapons and high-capacity magazines. Walmart, the biggest gun seller in the country, took somewhat similar steps, including stopping the sale of toy and air guns.

A number of other companies – including Delta Air Lines, Hertz and MetLife — disassociated themselves from the National Rifle Association, which has played the leading role in keeping many state and federal lawmakers from passing common-sense gun laws that many of its members support.

More can and should be done.

After all, 20 first graders and six adults were massacred by a  gunman with an assault rifle at Sandy Hook Elementary School in 2002 and essentially nothing happened. Since then there have been at least 239 school shootings nationwide.

Yet, after previous shootings most lawmakers and big businesses offered nothing but thoughts, prayers, and lame excuses. But Parkland was a shock-the-conscience moment.

"We have to help solve the problem that is in front of us," said Dick's Sporting Goods CEO Ed Stack, whose company sold the Parkland killer a gun last year.

Credit the Parkland teens who survived the shooting at Marjory Stoneman Douglas High for starting a movement that forced corporate America to finally take notice. Since the Valentine's Day mass murder at their school, the students have sparked a powerful grassroots movement that has caused big businesses and lawmakers to sit up and take notice.

Armed with little more than their smartphones, the teens organized marches nationwide and within weeks forced Florida lawmakers, who have long been the leading lackeys for the NRA, to pass the first notable gun reform measure there in decades. When Fox News host Laura Ingraham mocked Parkland shooting survivor David Hogg, he showed her how adept the teens are at mobilizing.

Hogg tweeted out a list of Ingraham's biggest advertisers to his 600,000 followers urging them to call the companies and express their concern. Several companies quickly pulled their ads from Ingraham's show.

In the 1980s, college students helped lead the movement to end apartheid in South Africa through protests and by pressuring institutional investors to divest in companies doing business there. It was a long fight that helped lead to the dismantling of apartheid and Nelson Mandela getting elected president in 1994.

Similar pressure is being applied to large investors who own shares in companies that manufacture and sell guns. Lawmakers in several states, including New Jersey, are moving to restrict employee pension funds from investing in gun makers.

Sustaining the effort to implement common-sense gun measures will only come about through more pressure on corporate America and the voting booth.