How long do you have the kids each day? Do you have full flexibility on how you set up the class and run it? What activities do you HAVE to do with them (group reading/teach a particular pattern or letter each day...?) What kind of English level are they at right now?
Here some fairly random ideas.
You have to go in believing 100% you can have the kids under your spell, and that you have a well-planned, well-balanced class/day prepared. You need have real strategies for getting the kids to sit where you want them, to be calm when you need them to be, and so on. And you need to find enriching things for them to do. Battery9's ideas for dividing up the class into smaller groups is necessary to get things done quickly. It stops chaos when you want to hand out scissors, paper, etc. Have a weekly leader for each group and make them responsible for having all the kids say a pattern such as "Thank you for the scissors," when they hand the others the items. Little things for reading time like, letting the back row sit on chairs so they can see, using big books, asking lots of questions about the book before you read it to let the kids get what they want to say off their chests, and sitting quietly yourself when it's reading time rather than shouting "Sit down, reading time!" help a lot. If you are using a reader, photocopy it to A3 size so all the kids can see it. If you have a projector, take photos of each page of the book without the text and project it on the board. Ask all your target questions before presenting the real book with text. After you read it, have them put the story in order. If it's a rhyming book, play a game with hula hoops where if two words rhyme, they jump in the hoop, if they don't, they sit on the floor. Keep each individual activity to no more than around 7 minutes at first. You might be doing "rhyming" for thirty minutes, but do at least four related activities. Make sure you model very clearly or kids will blank out if they don't understand.
Are there activities prepared for when the kids have down-time such as waiting for slower finishers? You can get heaps of ideas by searching for "Homeschool activity bags" or "Toddler activity bags" online. These are little ziplock bags of things kids can get themselves and play with while they wait. Maybe a set of toy animals and beginning letters so they have to match the animal (horse) with H and so on, or a number card and little blocks so they can see the "1" or "one" and they put one block on it. Present them as a reward they get for working nicely and cleaning up their space.
If kids are giving you the "I have to go to the bathroom" trick, just make one bathroom pass for boys, one for girls. They have to take it when they go to the bathroom. That way, only one boy and one girl can be out of the room at a time and you don't have to spend lots of time discussing or arguing with the kids.
Is any of that helpful? I'm sure others have great ideas, but I think you need to narrow down your questions a little bit to get help relevant to what you are doing.