Get them familiar with the school: Take them to the school and walk them through it. Talk to them about school routines, the amount of time they will spend there, show them the classrooms, playgrounds, library, computer laboratory etc. If they are continuing in the same school then you need to emphasize the differences this year will bring.
Talk to them about their first day: Familiarity makes it easier on them. Talk to them about the various classes and the routine they are expected to follow. Emphasize the exciting parts like how they get to eat lunch with friends, play in the bigger ground etc.
Let them pick up the school supplies: Ask them to select their own pencil box, lunch box, pencils, and satchel. It will add to the excitement and your child will feel responsible and important. If the school issued books for the year before vacation, get them familiar with it over the summer vacation. Ask them to pack and organize the school bag for the big day.
Get into a healthy bedtime routine beforehand: Make sure bedtimes are set and your child is used to getting up well in time to get ready for school. A well-rested child will be a happier and more compliant child.
Dropping and picking them up from school: The school would have sent instructions about this. Usually, you are expected to drop and pick up the child for the first few days. Make sure you reach slightly early to pick them up so that they are reassured as soon as they come out and there is no chance of anxiety and panic of any kind.
Keep communicating with your child: Ask them about the first day at school. Be specific with questions. Who did they talk to? Who did they sit with? What song did they sing? It is natural for your child to refuse to go to school once the initial excitement wears off. It might be a good idea to point out the other children who go to school and how it is normal to do so. If you sense that something is amiss, do not hesitate to meet and speak to the teacher. Remember, they handle many such children every year.
Stress on the excitement of growing up: If there is a younger sibling at home then make sure you let the older one know how boring it is for the younger one to be at home all day with you, and how both of you are jealous that the older one get to go to school. When they back make sure to spend some exclusive time with them over a snack and talk to them.
A little organization can go a long way in easing their way into the new school and change those tearful glances to cheerful eyes in the morning!