The Poo is to the left of the Port-O-Potty's / Outhouse, on a rock.

On the map house, you will need to go upstairs and find a Kids room. Once in the Kids room, go to the table in the middle and there will be the Poo on the plate.

On Abbey, you will need to go to the far top left of the map. The poo is right behind one of the exit doors.
On the second one, you will need to go to the far left from the Survivor spawn.

On the third one, you will need to go to the garden, which is beside the Church. Credit for this one goes to Døømør

On the map Farm, First you will need to go into the Green barn, Go in the corner where the cabbages are and the Poo is on top of a plate.

On school, The first Poo is downstairs, beside the stairs in the trash can.
The second Poo Is upstairs, beside the Gymnasium Balcony.

The third Poo is right outside of the Computer Room upstairs, it is hidden inside of a slighty opened locker.

The Poo is in the corner of the map beside the generator, inside of the Couldron.

Check back each image, my cursor is hovering each of the Poo and each of the poo is highlighted yellow.

It is the smallest prop in the game and can fit in spots some other small props cannot.