Questions about air-quality testing in high school
First off the acceptance levels the first time are way lower then the second time, you should ask why there is a large difference. (I have no clue, it's quite important since the second time those limits are NOT met!)

I found NO acceptance level for the chemicals (long term exposure.) 
THE most accepted guidelines are usually set by the world health organisation and even they do not dare to set limits since it is difficult see http://www.euro.who.int/en/health-topics/environment-and-health/Housing-and-health/publications/2010/who-guidelines-for-indoor-air-quality-selected-pollutants
For common benzene they wrote a small book.

But to put it in perspective, I think that you inhale way more of those chemicals during filling your car. Then staying in the classroom for a week ;) [Citation needed!]
Edit: the concentrations are actually all more elevated then the averages mentioned by literature. Can we please have a copy of the raport? Next time it might be better to measure air quality according to the WHO guidelines since we simply do not know what we are looking at.

"First, the first round of tests analyze specific areas in the school, but the second does not identify any area.
Both rounds seem to have measured almost exactly the same levels."
I agree, this is weird. You should ask where and how this is sampled. But there are regulations for the sampling, let's assume they are professionals and based on previous results this is a worst case measurement.

"The recommended NIOSH residential levels are measured in ug/m3 in round one testing, but ppm in round two. In round one, for example, the recommended maximum for benzene is 0.360, which according to this tool, translates to 0.00036 ppm. However, on the second test, has a recommended maximum of 0.1 ppm. Also, the same calculator translates benzene’s if/m3 of 8.9 to 0.0089 ppm, but in the Test two results, it is translated to 0.0028."
PPM is a horrible unit without actual dimensions just like percentages. Are we talking about volumes, weights , molars or a mix? Anyway, just use the ug/m3 since that's what really Is measured. (I you like you can see the right conversions inside the WHO document http://www.euro.who.int/en/health-topics/environment-and-health/Housing-and-health/publications/2010/who-guidelines-for-indoor-air-quality-selected-pollutants but that's only if you like math ;)

"Finally, parents are simply unfamiliar with these chemicals and what the levels imply, and how they affect teenagers. It is hard to fight with you can’t see or smell."
I totally agree! But don't underestimate the nose ;)
I GUESSE, looking at the numbers there is no extreme dangerous exposure. The second report concludes the the same. The world health organisation does not exactly know what levels are really exceptional dangerous, therefore it's by "law save" as long as there are no observed health problems. But just ask the professionals ;)
This is where my field ends, it's up to you to tell the right people the right information and ask the right questions, (you are probably way better at that then I am ;) good luck!!