Be careful what you ask for
From what I read on here the assistant will just undermine you at every turn

I have Chinese teacher present in most of my classes at Public Primary School. Sometimes (especially in Grade 3), Chinese teacher is translating lesson to kids.

At two Training centers previously, I also always had Chinese teacher in the class.

I usually ask to be alone with the kids just in first two weeks.  

Why do they let you work alone? Chinese teachers usually learn English, while present in the class. Just tell them you need help, because kids don't understand you. Once, you have TAs in, make them do whatever you want. Not 'whatever' they want. You are an English teacher, and TA is in for your help.

I don't know of any school in this area that does not supply an Assistant Chinese teacher. It's next to impossible to teach kids of that young age who don't understand basic instructions in English.

Ask for help. Even with my smattering of Chinese I need an assistant.

Anything else I can help you with? Happy to be of service.

Here's a long and complicated answer. The TAs are supposed to be there to translate and make your instructions clear.They are supposed to follow your lead.

However, you'll run into TAs (perhaps at management's prodding) who think that they are better qualified to run the class than you (either because they know fear and intimidation works or because - hey! You're a foreigner and what the hell could you possibly know about educating Chinese youth?).

I've had TAs disappear in the past simply because they wanted me to lose face (they hated foreigners and English) and some who thought it was simply redundant to have two teachers in the class and their time could be better spent in the office chatting on QQ, playing games, napping, or otherwise f*cking the dog.

Plan your lessons ahead of time and tell your TA what role you want them to play You'll find that it makes for smoother sailing.

  I teach mostly kids from between 7 and 12, but until my Chinese was good enough that I could conduct the class on my own I always insisted on a classroom consultant. I don't honestly know how anyone could manage without one. 

  My advice with teaching kids is to set up a reward scheme they will be prepared to work for and that you can deny them individually as punishment should they get rambunctious. I literally only need to count to five in my lessons and they are sitting silently by the time i'm finished. But if they continue to act up you deny the whole class. Peer pressure pretty much does your job for you after that. I've got a personal system whereby students earn stickers they can collect in an album under various topics (food, animals, political leaders of the 17th century, etc), plus a small sheet of stickers each and the chance to take part in a raffle at the end of the lesson. Collect 100 stickers under any subject page and you can choose something from the raffle bag. All this stuff costs me about 5 yuan a lesson but it makes lessons move smoothly (no classroom consultant in my classes) and they work hard for the rewards. I wouldn't do without it.

How's your Chinese?  If it's not at least in the pretty good category then the little kids won't be following you at all, in which case you will love having a TA who can translate for you.

Tell the school you want one, or else!

BUT....you're the boss of what the lesson's about.

Phil, some assistants I had were great, some were good and some were mediocre (one I had was scared of children - she took the job because she thought it would make her look more respectable). Even the less useful ones were better than nothing, as last-resort translators if nothing else. 

Martian's advice was great - when I taught kids, I had a similar reward system going. Top kid got a sticker. They seriously do compete to be number one like their wee lives depend on it. 

My experience is that the assistant is for domestic violence purposes. I.e.: she will beat the students if they don't obey you. I'm more lenient; I beat the assistants for being c-bags.

Like MissA, some assistants were great (I loved working with them!), some were good, and some were mediocre. Then we had this one complete and utter bitch that hated the fact that I was teaching English and not her. I had my pregnant wife beat her up and she never back-talked me again, but you could see the rage in her face every time I walked into class.

My best advice for teaching kids (this is what MissA gave me a while back) is to just act completely and totally insane. Go full-retard and start entertaining them... but make sure they actually learn English. You won't really need to teach them, but if you can drill proper pronunciation into their skulls, they'll never forget it. Pay close attention to "teen vs. tee," "th" sounds, the letter "v" and other things they suck at. Make them learn it. Drill the "v = w" non-sense out of them.

I worked with kids between 3 and 6 years old for a year. I never had an assistant. I never used Chinese (though there were always two other teachers somewhere in the classroom, but if they translated I stopped them) and I didn't have a reward system. Kids that young are programmed to do as the adult does, and learn like sponges. Translating the lesson will never be as effective with little kids as using pictures (photographs) or scale models that are as close to real life as possible, and when possible the real object. For example, an apple. The kids all want to touch it too, and smell it, so you raise your own hand, the kids will follow suit, when you raise your hand you also say "raise your hand" some will say it too, but it doesn't matter if they don't, they will eventually understand so after a few lessons just saying raise your hand is adequate, you no longer need to raise yours. Anyway now their hands are raised, you choose a kid, probably choose one with slightly better English because he is now the example (similar to you raising your hand to begin with) ask him what are you holding, what color is it, can you eat it, after he's answered you can ask would you like to hold it, he'll say yes, you can teach "yes please", if you will he holds it, you tell him to smell it, he doesn't understand, so you hold it to his nose, then you ask him to sit back down, now you can ask who wants to smell the apple, if you want to smell the apple please raise your hand... 

Always push for full sentences when asking and answering questions, but never force. Number one rule is to always use full sentences yourself (if you ever listen to yourself you will realise how lazy native speakers are when answering questions, you'll rarely get a full sentence out of us.) because kids learn from example, not translating. 

After 5-6 years old it's a bit different because at this point they start to realise that they don't actually speak English and so it takes a bit more effort.

Key Points:

Body Language, set examples, when introducing new material the preference is for real life objects, if unavailable then go for scale models (best if your and isn't bigger than your elephant) and if you haven't access to them either then photo's are your best bet. AVOID cartoons and unrealistic imagery.  

These tips are from my training for a Montessori education. Definitely an education system I would vouch for after working in both standard and Montessori Kindergartens. 

As for discipline I never really had a big problem, I knew who the class disrupters were and made sure they never sat together, if anyone was too rowdy I removed them (they went and sat on a chair in the corner for 10 minutes after which I gave them the choice of staying there or coming back, always came back) and if all else failed I just put all the materials behind me and the children knew what that meant. Whenever it came to that the head teacher would take a note and be sure to give them a grilling next time it was her turn to hold an activity or group lesson. 

My classes were 30 minutes with 18-25 students, 8 of these lessons a week. Though I did one on one with each of the students for 10-30 minutes every day too and on odd days supervised the younger ones sleeping, even days I was with the older ones who didn't nap and we would go out of the kindergarten grounds on mini field trips to learn about the trees and rocks and ocean or whatever, sometimes just took them to the playground. So I think having such a close relationship with the students helped in keeping them in line. 

Actually, my three assistant are very, very helpful.  They are seasoned, mature teachers very adept at handling most situations.

My lead assistant was recently out on a prolonged sick leave and I was able to handle the classes myself, owing probably to the fact that I can speak "survival" Chinese and owing to my girth and red hair, I think, too.