For typical altitude clouds are classified as: cirrus, cirrocumulus, cirrostratus, altocumulus, altostratus, stratocumulus, stratus, nimbostratus, cumulus and cumulonimbus.
Like all classifications can be very boring for children, and this is a very good idea to be implemented for field test and store concepts in an active and fun:
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If you want to implement the project with your children, photographs and classifications of clouds you can print from here:
http://www.metoffice.gov.uk/learning/clouds/cloud-names-classifications
https://en.wikipedia.org/wiki/List_of_cloud_types
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml