Allow the children to to be accountable. One of the things that many children who start out in traditional classrooms find disconcerting about Montessori classrooms is the wide selection of lessons and options that they have on any given day. If your child is having trouble focusing his energy because he is used to being told what to do, work with him to decide what types of things he might do each day. Many Montessori classrooms use a lesson plan that designates what types of lessons a child might do--math, language or practical life, for example--but do not specify which lesson. If your child is not using one of these already, ask his instructor if they might help him draw one up so that he has some guidance for his day and can report in when he has completed a task. As he gets more used to the lessons and the freedom, this will become less necessary.
Help your child set goals. Set goals for the day together. They may be simple goals that can continue from day to day, such as introducing herself to a different person at lunch each day, or they may be more specific goals having to do with completing work or learning a new lesson. Ask your child's instructor for help with setting these goals so that they are not in conflict with any classroom rules or principles.
Answer questions directly. When your child asks you why she is in this new school or why she cannot just go to her old school, be straightforward. Tell her that you have selected the school that will help her learn the most and have the most fun during her learning years. It is obvious to you that you have enrolled your child in the school that is the best for her, but you may need to clarify this to her.
Give him independence at home. Montessori schools often provide lists of household tasks and chores that the school thinks are age-appropriate for the students. Montessori classrooms are, in large part, run by the students. This includes cleaning, organizing and even some lesson selections. Find out what your child's responsibilities at school are, then allow him to have the same responsibilities at home. This will help him start to contribute to the upkeep of his own household and make the chore more familiar, which will help him feel more at ease doing it in the classroom.
Give her time. As unpleasant as it is for a parent to hear, your child may not immediately take to a Montessori classroom setting, particularly if she enjoyed her old traditional classroom or had lots of friends at her old school. You will have to be patient and do everything possible to help her become accustomed to the new school. Do not give up if she is not ecstatic to be heading off to school each morning after a week has gone by. It may take several weeks for her to become completely comfortable. Talk to your child's instructor to see how she is behaving at school, as you may find that most of the complaining actually occurs at home, while she is making friends and learning as usual in the classroom.