Mounting photographs on board?

I spent an afternoon this week doing some photography with some 10 and 11 year olds at my sons' school.
They took macro shots of shells with a wide aperture and the results are really really lovely.

I have had them printed and we are going to display them at a local art gallery.
They are 5x7 and I have 25 so we were going to put up a grid of them on the white board.
I think it will look more effective if they are mounted on something so that they raise up a little.

I did this years ago with snaps for our kitchen. I mounted pictures (of the kids messily eating) on thin mdf painted black and they look great.
A bit of googling suggests that foamboard is regularly used to do this.

Has anyone got any advice on doing this?
How I then hang them on the wall. What I need. Where I can get it from cheaply. Any better ideas.

Some of the photos in case you are interested:

These are really nice Em

Re mounting them - I think your own idea is probably best, use a thin MDF that you can just place wherever you want. That way you can easily remove it without having to take it apart

I'd like each picture individually mounted on something so they each stand proud.
Does that make sense?

Ah right.

I'd consider having the black mdf as usual, then smaller ones in a different shade slightly larger creating a border for the photos themselves. That will give them a raised/elevated position and should look neat

Foam board is what you want yes, don't tell everyone, but I buy mine at the local college, (as well as my mounting card) as it is around a third of the price that it is in art shops

Me, I'm a student yes, just because I look nearly 50 hahahahaha.

Alan.

So I could cut 24 pieces of foamboard to 5x7 and mount the photos on them- but what do I do with them next? How would I attach them to the wall?

You stick them to a nice big piece of mounting card, you can buy this from your local art shop, or college. if you have 24 5x7 you might need a few pieces You can buy it in many colours tool

Alan.

Thats a great plan and the Headteacher likes it too and is off to the Range to pick up supplies.
Thanks!