What is the best way to encourage native Arab children to speak better English from an early age?

It is important to teach them how to like and love any new language then there are are a lot of different ways begining with the new technology that they have to day....

Learning should be interesting and fun. Start teaching from easy to difficult, from concrete to abstract.

Like any kids - simply start speaking English to them on a daily basis

Speak English to them on daily basis

Very good answer  denis popov 

In order to do that you need to create an atmosphere within the classroom where pupils start loving and using English as much as they can. Audio visual aids are very much recommended. You can't make students practice English language. You should play a role of facilitator.

If the teacher tries not to use  the mother language as possible as he can inside the class and encourage students to communicate with him and with each other freely using English language.

After Arabic

English can be done

For children: attract them by any thing and depend on the situation.

I think anything comes with practice especially learning a language.... so start speaking with them daily for a couple of hours in English (but let me point out something don't always do it to the extent that they become weak in their own language...balance) Of course this requires correct pronunciation and good grammar to build the correct and strong basis