The National Rifle Association offered free help to schools that hire armed guards to protect their students and backed expansion of the federal government’s list of banned guy buyers, but it defiantly warned Thursday against Washington’s overreach after last week’s school massacre.

Executive Vice President and CEO Wayne LaPierre said FBI bungling, mental illness and lax school security were at the root of the Valentine’s Day shooting that left 17 dead at Marjory Stoneman Douglas High School. He said the solution is better protection, not tighter gun laws.

“Our banks, our airports, our NBA games, our NFL games, our office buildings, our movie stars, our politicians — they’re all more protected than our children at school. Does that make any sense to anybody?” Mr. LaPierre told a Washington audience at the Conservative Political Action Conference, a gathering of grass-roots leaders on the right.

His annual speech to CPAC is always compelling, but this year’s version was all the more so because of the timing, giving Mr. LaPierre a chance to respond to the NRA’s critics, a group that now includes many of the students who survived the Florida shooting. Some of the survivors are leading a nationwide effort to enact strict controls on what weapons can be bought and who can buy them.

Mr. LaPierre, though, warned against “opportunists” using the tragedy to advance a “socialist agenda” that begins with denying gun rights. He said the response to the shooting should be careful and targeted.