from NVQ/SVQ Level 3 Teaching Assistant's Handbook:
It is important that all staff are consistent when managing pupilsā€™ behaviour. Children need to have boundaries that they can understand and which
are regularly reinforced by adults. If it is not clear to them how they are expected to behave or if adults give them conflicting messages, children become confused and upset, and find it hard to know how to behave next time. Although all children will test boundaries for behaviour, if they are met with the same response each time they will be less likely to repeat it. Rules should be appropriate for the age or ability of the child and the language used should make the expectations of adults clear.
When managing pupils behaviour, be careful of stereotyping or making assumptions about how they will behave. If pupils are expected to behave well or badly, they will usually live up to the expectation.