An explanation (by Nanites)

You walk into a almost empty room with just a red carpet, a lcd screen on the wall, a wooden door with a window at the middle and close to the bottom that you can't see through and a good shaped hole in the middle of the door. You start to walk closer to the door but stop when you hear a man who just appeared on the lcd screen.

'Hello students! You may not know me but I am a newly announced Minister of the Fertility. As you probably know there is a large scale problem with birth caused by an accident with the vaccines. To prevent the extinction of our nation we had to take drastic measures to increase the birth rate.' He continues.

'Starting today, everyday you will be having what we would like to call 'fertility seances'. This is a special room designed for this purpose. It features a one-way mirror in the middle of it. Some of you may have noticed that there are two of you inside.' He finishes this sentence with a uncomfortable smile.

After hearing that you cover yourself up quickly and walk up to the one-way mirror to inspect it some more for a reason unknown even to you.

'Studies have shown that ejaculating once a day for a week increases a chance for impregnation three times. This effect doesn't last long though so the men have to keep doing this. Now I will tell you about the rules.' You listen carefully as he explains