An updated list derived from further discussion:
1. Arm qualified school teachers / staff that choose to carry a firearm.
(Allowing them to use their own firearms, and possibly providing firearms to others who don't already have their own. THIS IS NOT MANDATORY FOR ANYONE.)
The following information tells how to do this within current Iowa law.
https://law.justia.com/codes/iowa/2014/title-xvi/subtitle-1/chapter-724/section-724.4b/
724.4B Carrying firearms on school grounds - penalty - exceptions.
1. A person who goes armed with, carries, or transports a firearm of any kind, whether concealed or not, on the grounds of a school commits a class D felony. For the purposes of this section, school means a public or nonpublic school as defined in section 280.2.
2. Subsection 1 does not apply to the following:
a. A person listed under section 724.4, subsection 4, paragraphs b through f or j.
b. A person who has been specifically authorized by the school to go armed with, carry, or transport a firearm on the school grounds, including for purposes of conducting an instructional program regarding firearms.
2. Provide and require free, or low cost, annual firearm training for all teachers / staff participating in #1.
(It would be provided optionally and promoted for all others. THIS IS NOT MANDATORY FOR THOSE CHOOSING NOT TO CARRY FIREARMS.)
3. Provide free or low cost annual self defense training for all teachers / staff.
(I can make a strong argument for making this mandatory for ALL, but am willing to leave this optional, due to all of the push-back within the previous discussion. THIS IS NOT MANDATORY FOR ANYONE.)
4. Convert all non-main school building entry points into Emergency Exits ONLY, install electronic/mechanical devices to prohibit unauthorized entry, and set them up to set off alarms upon unauthorized use.
(Similar to how many office buildings, and stores, are designed today. Suspend / expel those who choose to trigger false alarms.)
5. Implement security screening areas at all main school building entry points, including, but not limited to metal detectors and armed security guards.
(Clearly identify what items are prohibited and set size limitations on book bags, etc. I would suggest leveraging National Guardsmen/women as much as possible, where available, at least initially.)
6. Install simplistic internal door locking / barricading systems that can be engaged manually from within each classroom, and/or even electronically, linked to the alarm system.
(Suspend / expel those who choose to activate these devices in non-emergency situations.)
7. Hold random Active Shooter drills periodically, similar to Fire and Tornado drills.
(The more these are practiced, the better prepared everyone is for a real-live situation.)