Maybe one of the most challenging activities for an Art teacher is to build masks with it's pupils...how to encourage the littel ones to create imaginary masks, beggining with drawing, using paint, textures and modelling shapes in the age of computers and Internet!!! How to be competitive in this world full filled with images, models and with little space to let the children to fly with imagination????
It's possible indeed!!! Here some examples of projects dveloped in the Peruano Britanico school at Lima Peru....ages ago!!!
Despite at the moment I am not teaching Primary, but overview the programs for the 3 levels, working with the little ones was always fun...a complete challenge on every single session on wich as teacher I have been requested to show results to my puplis and show them all that Art is a serious bussiness that request from all of us concentration, imagination and hard work in class.
Imagine: developing a mask since a paper balloon...wrapping the ballon with glued paper (5 coats) and when it's dried and hard enough you can start building beak, feathers, different volumes and shapes with modelling paste.Finally , when all the details are completed, kids can paint.
It sound easy..but it's not. 
I always loved this long term activity where my students have the chance to use different resources and media. The activity demanded to all of them to learn new skills, techniques and proficiency when improving their projects.Imagine to develop something that you see just in your imagination....and you must transfer this iamge to 3D.
When I teach Art always I present a challenge to my pupils. A show them a new problem to solve.That's key for developing creativity and request from us to use our imagination, sometimes the process will be hard because as children they must THINK. And thinking is not easy for people. Thus, Art request from the little ones to think every moment along the session. This ideas will be transformed on shapes nad colours.
Finally , the masks are not the real representation of animals(birds, cows, cats, etc) these are indeed the representation of what children see, of what they perceive the world. That the most funniest. I remember my Art classes, plenty of challenges, imagination, some times frustration ...but always with children looking themselves as creative persons.