What do I do?!? Teacher Frustrations

OKay so yesterday I started in on a two and a half day treck with one class while their teacher is gone. I thought yesterday didn't go so well because they had their teacher for the first half of the day and so I just thought it was them thinking they could get by with things because she wasn't there. Today... they start out pretty good and we have a couple of rough parts through out the morning but I thought it still went pretty good. Then they come back from lunch and oh my goodness eveything falls apart- Yesterday I did what she said and sent them by tables to the bathroom after lunch but it took longer then I would have liked so today I take them as a class (as I saw another teacher do) and it doesn't take long before three boys come out saying some boy threw another boy's shoe in the toilet and the story proceeds to change several times. So we go back to the class and have a discussion on being respectful and kind and so forth. It seemed to work for a few minutes but then they start in again. It is like they don't even hear my voice! I don't like to yell, I think you should be able to control children with out yelling at them, but I even raised my voice today and it didn't work! I have tried her way of getting their attention (counting 1, 2, 3, and they say it back to me) Nothing! I try it my way (start out with five marbles and it can go up or down from there!) Nothing!!! Oh yeah I should explain the marbles-if they get the jar full of marbles they get a halloween party-so I told them we will start the day with five mables and it can go up or down from there depending on how they act. Yesterday it worked ok but today.. no affect. I am at my witts end-I have NEVER had this much trouble with kids!!! The teacher across the hall (who is really good friends with the real teacher) even came over, sent me into the hall, and proceeded to chew on them like crazy-there were a few that were crying when I came back in but once again that only lasted for a few minutes before they were back to ignoring me again. It hurts because I have never had this much trouble with kids and I have somewhat of a reputation in this school-so far every teacher has liked my work-I even have teachers telling other teachers to request me and I feel like I failed those teachers today!!! I know that I can only do my best and that's all that counts but I try really hard to watch other teachers and find out what they do trying to get ideas cause kids are so very different so they require different forms of rules and discipline! I even try to make sure I do what the teacher that I'm subbing for does so that it is close to their routine but I have no clue what to do anymore and I still have a full day on Monday! So for whoever reads this any suggestions are welcomed. Please pray that I will have the patience needed for Monday and keep a meek and quiet spirit-these kids still need me to be a godly woman and show them the love of Christ!