OK, I'll comment both here and on your site. I should point out that you might want to give more info. What size are the posters? I can get a fair idea from the posters, but what does NSPCC do? And what does it stand for?
Age: 25 and I have experience as a designer.
Poster1: Type is too spaced out, and the font choice and font colour don't really work. The type doesn't flow as it should. Having each word separated like that, it's almost telling you to pause between each word. Also, it's ambiguous as to whether it's word of hope, or a command. The black spot over the face doesn't work either. If the model didn't want to have their face shown (or if it's for security reasons), don't shoot the model's face. Maybe a close up of the body (and specifically, the body language) would have worked? Maybe you could have shot them from behind? Creative lighting would have helped with the mood here. I just don't think it looks like they're suffering. Plus, the pink might add too much warmth to the image, which doesn't really add the right mood.
I think the logo is too large, and would probably need a little more white space around it. Either this, or create a large white panel running the width of the poster, with the logo in that (so essentially, the poster is divided in two. Maybe 4/5 for the image, 1/5 for the white panel with logo and info) Don't neglect using white space - it's powerful, and can really grab the viewer's attention.
Poster2: Pretty much the same as above. The logo size is improved, but just looks tucked away in the corner, as if the viewer isn't really meant to pay it much attention. It's good how the text kind of leads the eye down to it, but again, the text needs work. The "?" is getting cropped, so watch the spacing there. The font is a little better, but again, the colour isn't too good.
Something you might want to consider - does this organisation only deal with youth? If not, a more 'anonymous' image might help - such as the model being shot from behind. This way, the body language speaks, but there is no face, suggesting it could be anyone. You, someone you know, someone you've seen etc. Putting a face to the image narrows down the target audience too much. Also, it's much tougher to get just the shot you want, as faces are hard to capture with the right expression, unless the model is very talented.
Poster3: Again, same comments apply to this. I think the photo is stronger, and the wording is stronger as well, but the font, colour and positioning of the type let it down a bit. Just for kicks, have a go at the white panel down the bottom and see how it looks. It will allow you to put the type down there, giving the image more room to breathe and convey more power, the information will be organised and easier to follow.
Conclusions:
If you have time for a reshoot, I'd try some new things with the photography. Maybe some darker settings, different angles. Play with depth of field - a close of of the models face, which is out of focus, but their hands are in focus, maybe dirtied or with scratches. If I knew the organisation I'd be able to help out more.
Scout around for some locations that you can easily shoot at, and be able to spend a decent amount of time shooting at. How does the location look at different times of the day? Sketch out some ideas once you have a few locations. Remember to keep information organised. Don't space out type as the flow and meaning are lost. And if something doesn't work, find a creative way around it.
Another important thing to consider - how are real posters like this done? What makes them work? Use these and other posters that inspire you to get some ideas for layouts, fonts and colours. Consider the target audience and desired effect at all times though, as this will help you define the theme.
I don't think you have any problems with the photography side of things. Especially in the 3rd poster, as that's the strongest image. I think the type is letting you down a bit. Keep it closer together, and all in one line, as it is a sentence after all.
...wow, longest post ever, heheh
