Some nice rendering there ..Cool color balance..there are some things which needs to fixed imho..
1.Modeling--Check the overall proportions of every objects ..they seem a bit off.Pay special attention to chairs and book shelf.
2.Texturing and Materials --You need to work a lot on this part.Wood mat you'd used is looking very basic.Add some glossiness. Same goes for wall.You can use add nice educational related images to it.
3.Lighting-This part needs some tweaking. Window part and ceiling are looking so bright and burnt off and still, the entire classroom is not that bright ??Use Exponential color mapping and play with the multiplier.
P.S --you can light up those top lights
.It will add realism to the scene .
That's it..Keep working and best of luck.