This can be done in many different ways and there are many good scenarios to communicate this message. A general rule of thumb for positive encouragement is that you can almost never give enough. In light of this, let me give you a few scenarios that might be particularly appropriate.
First, you can communicate that a child and parent belong on a daily basic by care and love. People catch these things almost intuitively. So, if you care for someone, they will know it by your language, attentiveness, body language and the like.
Second, schools have parent / teacher conferences. This is another time when you can communicate your care and concern as well. By your thoughtfulness, you will communicate that this family belongs to the school.
Finally, many schools have dinners and informal times where faculty and families get together. In this informal atmosphere, you will be able to share on a casual level. This can be a very good time to make all feel welcome. Also it is a great time for people to get to know you.