Please explain this to me I’m still lost on this thing.
You take 20 people and put them in a room for 5 hours - all masked.
Halfway thru this time together, they all take of their masks for 30 minutes.
Are they protected from transmission?
		
		
	 
You do different things when they're eating vs when they're doing other activities.  There's not one silver bullet, you use the item that's appropriate for the circumstances of the moment.
	
		
	
	
		
		
			I have no idea what happened at your school, but at ours the days where shortened so the kids would not eat lunch at school.
Why?
The school board determined there was NO SAFE WAY to have a lunch period.
		
		
	 
They determined there was no safe way based on all the extra additional restrictions and trade offs they made.  It's not an absolute, they just didn't like any of the trade offs.
	
		
	
	
		
		
			Yeah actually it does. 
To bad the people in power don’t have the guts to make it happen.
		
		
	 
There's no perfect one to solve them all.  Even vaccination for every student.  Since, vaccination for every student in every grade level before the school year starts isn't possible.  I mean, are we just going to guess at the correct dosage for a few million 4th graders?  What about kindergarteners?  In a High School, sure that would be the best solution.
Everything is a trade off.  Which mitigations do you take in a specific circumstance vs what you're trying to achieve and what you're willing to adjust.
So, for 30 kids in 4th grade you've got a few different time frames.
- Transport to/from School
 
- Classroom Learning
 
- Gym
 
- Band/Chorus
 
- Lunch
 
For 1 and 2, mask them up and pack them in like normal.  That's probably a good trade off.  Adding distance for 1 destroys capacity faster than it reduces risk.  Distance in 2 requires staff faster than reduced risk.  Remote learning is really just max distance, to a point where distance itself is now creating its own issues.
For 3, go outside whenever possible.  When not possible, ventilate the space and distance.  When that's not possible, have health class instead.
For 4, do it outside.  Just like Gym.  Book leaning when you cannot.
For 5, you've introduced a new requirement.  You cannot cover your pie hole and put pie in it at the same time.  So, now you're back to ventilation and distance.   Put half the kids in the cafeteria, spaced out, with ventilation.  The other half in the classroom, now spaced out since there's less of them.  Still not enough space, use a gym, auditorium, travel trailers, party tent to create more space.  Just because you've eliminated the use of a mask doesn't mean you've eliminated all other mitigation options.  They're all just harder than a mask.
When your board determined they couldn't do it, what they really determined is they didn't want to create the space and extra staff required to do it.  They correctly determined that packing the normal amount of students into the cafeteria to each lunch was a bad idea.
Even all those different choices also depend on the current level of community spread.  If it's low enough locally, then you need less of them.  If it's high enough, you need more.
They're all trade offs.
It's just like computer security.  You probably do unsafe things all day long.  You've determined that the mitigations you're taking are good enough vs the value.  Every link you click on could be to a phishing site to steal something.  You make a ton of judgements before you click it, your browser too, maybe your home router or work network does.  They're all trade offs vs the value you get from opening the web page at that link.  If you wanted to be completely secure, 100% safe from a phishing site, you would block all web browsing 100%, completely safe but no value.  That's an options for school kids too, stay home on the couch watching TV all day.  Not a lot of value from that though.