Not sure - we have "buddies" at our school where preps are allocated a grade 4/5/6 kid to look after them. They often become great mates and it means that the kids play across all age groups. It also reduces the incidence of bullying behaviour by older kids to younger kids. If it is just a 1:1 thing then it may be a concern but if it's a group or something that is promoted by the school then I probably wouldn't worry.