Choice of Language

Do all the students in my private clan have to use the same language. I have several using JavaScript and one using Python and I want them to all be in the same clan for easy monitoring. Is it doable or does the singleton have to switch?

It’s doable.
A clan can contain members that use any language. It’s also possible for a user to be in multiple clans.
Look at Example Clan: https://codecombat.com/clans/5530587343b9be960621cb64

Fun fact: My current favorite language is JavaScript, so the icon may not be 100% accurate. Also I started to use Pender mostly, so don’t rely on that Anya-Icon.

Which should be the best language to start? The age of our students are between 9 and 12

Python is a very good language for beginners: it’s easy to learn, easy to read, flexible, with lots of handy stuff. Very good for a solid basis.