Still not quite there...

Imagine if there was a “Decroche pas: Joue ton Role!” on it(sorry, it must be in French).
What’s wrong with it?
Do you get the point of it?

I’m afraid I don’t get the point, but I have never been good at understanding ideas of art, so the problem is probably at me :D.
Anyway, the desk (probably teacher’s) which is in right bottom corner of the picture seems wrong. Between left legs of that desk is probably some board (part of the left leg which is more in the middle of scene is not visible), but it has absolutely same color as floor, so I’m not sure if it is a board or not. But on the right side of the closest desk leg is different color, but the back right leg visible is. Also the back legs are shorter than those in the front, so it seems that desk itself is flying. I don’t know, it might be correct, but it looks weird. I would also turn the glossiness of desk a little bit down. The last critique is about the left part of right back desk, which is (probably because of post processing) a little bit moved up compares to the right part of that desk.
In summary I really like it even if I don’t get the idea, which I guess is the main point of this render.

Mmmh, a school class in a wind tunnel? Looks like a scene of a nightmare. What do you mean “what’s wrong with it”? A answer can only be provided if you tell us what your intention was … for example if your intention was to create a nightmare scene, then you are 80% successful, because at least I was able to recognize it immediately as a strange and bizarre scene. But if your intention was to create a normal school class scene … well then something is really wrong.

OK, so, this is a poster that is intended for kids that have left school, are in the tunnel, and the only way out is through school.
Yeah, I know…

Ah ok. That’s your intention. Then I have the following thoughts (I am no expert though):
If this poster is about the people at the back (now I know these are kids), then they should be more in focus. I rarely saw them at first (an the colors normaly darkens when printed).
So what i would suggest that make the figures in the background more visible. For example with an red lightsource at the ground where the kids are standing. This could be a grill in the floor. So that the kids are more present to the viewer.
Or a fan at the end of the tunnel with some light in his back.

How about that? I’m quite proud of it, I think that the mood is perfect…

Here is my interpretation: the classroom is in chaos, papers blowing all around, and it is a pretty sterile environment anyway, so the two shadowy figures in the background are leaving in disgust. The exhortation “Don’t hang up: play the game” seems like cynical adult advice admitting the process is a hazing initiation that is required for entry into society.

As Lux mentioned, it makes the classroom look like a nightmare, and, given that’s why your target audience dropped out in the first place, I don’t think this will convince them to give it another go.

OK, so, this is the focused critique category, so I’m supposed to take advise, but I have to say I completely disagree with you…
Have you seen comercials for drugs etc? They have a similar look. BTW, I can’t do anything about what is says, it has to be that according to the rules. And because I can’t change to idea now, it’s too late, could you post some “constructive” criticism?
I’m sure you ment well, but you’re not helping much.
And BTW, the colours are a bit changed in my post, no idea why, the metal looks purple while in my PC it’s blu-ish…

I am not the great CG oracle, you don’t have to agree with my opinions. I have seen commercials for drugs, and I suspect they work about as well as I think this one will. However, given the constraints of not changing the assets, not rearranging the scene, not changing the text…

Warm up the classroom colors. Change the chairs from green to wood tones. Leave the hellscape greens and blues in the tunnel with the two characters, but light them up so you can at least tell which way they are facing.

BTW, the focused critique forum is where we get to offer advice. Nothing says you have to take the advice. It is offered for your consideration, but we are not your taskmasters nor are we judging the contest this is for, so do with the advice what you will.

I gotta be honest here. I agree with Orinoco.

The way I see this image, is one of frustration. I see the two kids being frustrated and leaving school, giving up on the whole thing. I don’t see this as a way of inviting back.

I do get the point that you are trying to show…if you don’t finish school, you are on a narrower track. But, sometimes that narrower track is not uninviting, so to speak.

I guess, if you are trying to scare people to stay in school, maybe it works. If you are trying to get me to go back to school…it does not work on me. And, that advice comes from someone who dropped out of school, went back, dropped out again, and went back again. But, I didn’t go back because of any kind of issues. I went back because I wanted to, then I got bored again. LOL