I'm a bit hesitant to wholesale accept the premise that higher levels of inflammation are correlated with poorer academic performance.
This could be a chicken-egg paradigm; quite possible that some of the individuals with higher inflammatory marker counts compared to their cohorts were experiencing this
as a result of poor academic performance.
Psychological (or indeed any sort of significant acute or chronic) stress will lead to hypothalamic-pituitary-adrenal (HPA) axis over-activation. Many students have issues with time management or prioritisation skills. It's likely a chunk of these "inflamed" under-achievers have behavioural and/or social reasons for their phenotype.
Additionally, the association could be a red herring result. Students with pre-existing morbidities which predispose one towards inflammation (e.g.
depression, any of the various affective spectrum disorders like fibromyalgia, chronic fatigue syndrome etc.)
I'm also unsure why they've only used CRP, IL-6, TNF-a and total white cell count for their inflammatory markers... Could've thrown in erythrocyte sedimentary rate (ESR) at least (it's a better marker for chronic stress than CRP, for the unaware). Serum endocrine markers from the HPA axis would've also been a good idea to rule out confounding (discussed above).
IL-1 would've been a good inclusion as well given its' popularity in the literature. From memory, IL-1 plays a role in adaptive immunity signalling, so that (plus the HPA axis endocrine markers) would've nicely allowed the authors to build a more robust picture.
The data looks fairly clear, but the inferences look somewhat speculative without addressing some of the confounding factors here. Interesting nonetheless!