This is a great way of witnessing to your Christian faith. First, help your children to think through what it means that God forms each of us and loves us equally despite our differences. Help them to talk about the challenges and the blessings of doing life with people of different abilities. Help them find ways to talk honestly but not pejoratively (‘I get frustrated when Zach does x’, rather than ‘Zach is so annoying’). Reach out to the child’s parents at the school gates, or ask the teacher to pass on a note to them offering friendship and asking if there’s anything they wish their child’s classmates or friends would do or not do. Parenting a child with special needs can be utterly exhausting and all-absorbing. If you don’t get a reply from the parents, don’t take it as a snub, but an incentive to pray for the family, preferably together with your children.