Why disproportionate? Because the Marjory Stoneman Douglas High School Public Safety Act, signed into law in March 2018 soon after the Parkland mass shooting, had already established the "Coach Aaron Feis Guardian Program" named after the coach who gave his life attempting to shield students with his body during that shooting. That program gave school boards the option of allowing school staff members to carry firearms, excluding most classroom teachers who were not JROTC teachers, or current service members, or current or former law enforcement officers.
Last year's bill established a tough training standard, and left the decision to local school boards, both very good things. And since school staff who are not classroom teachers often comprise as high as 50% of the total, this approach was rational, if overly cautious, as school boards would still have the authority to approve or disapprove any applicant, without the no-teacher provision imposed by law.
The only change with the new law is that now all classroom teachers are also eligible to volunteer for the Guardian program.