*7.2. Lighting in Classrooms*

The lighting of school classrooms has changed from being mostly mercury vapor lamps that emitted a peak in the blue range, another in the green range, and another in the red range but with a wide spectral distribution, to being LED lighting, for which the composition of the light and the proportion of each part of the visible spectrum that the students now receive is different to that received from fluorescent lamps. LEDs do not emit a wide range of blue (blue LEDs do) but, as their emission is centered around 460 nm, even though the luminaires have a quantity of lx similar to that which would be obtained if a fluorescent lamp were measured with a lux meter, the effect of the proportion of blue on the melatoninergic receptors could be very different. Do those responsible for the maintenance of educational facilities understand the quantity of blue from the new LED luminaires they are installing and, therefore, the light that the students receive with the new LED luminaires, and how it differs from that which they received before?

**Author Contributions:** Conceptualization, D.B.M. and M.S.J.F.; methodology, D.B.M. and M.S.J.F.; formal analysis, D.B.M. and M.S.J.F.; investigation, D.B.M. and M.S.J.F.; resources, D.B.M.; data curation, D.B.M. and R.A.G.L.; writing—original draft preparation, D.B.M., M.S.J.F., and R.A.G.L.; writing—review and editing, D.B.M. and R.A.G.L.; visualization, D.B.M. and R.A.G.L.; supervision, M.S.J.F. and R.A.G.L.; project administration, D.B.M.; funding acquisition, D.B.M. and R.A.G.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** We are especially grateful to FUTTEC and the Universidad San Pablo CEU for providing us with the necessary resources to carry out this research. The authors wish to thank CEU San Pablo University Foundation for the funds dedicated to the Project CEU-Banco Santander (Ref: MVP19V14) provided by CEU San Pablo University and financed by Banco Santander.

**Conflicts of Interest:** The authors declare no conflicts of interest.
