How do I teach an 8yr old to block?

[wildbill]

My son has been taking TKD for two yrs. now . He has been sparring for 1 yr(& doing very well). He is an assistant instructor & primarily teaches other kids 9-under. When he spars he is usally put up against kids 9-12. His teachers want him to learn how to control someone with a longer reach than his & he is having a rough time. he's mainly taking (somewhat controlled) shots to the head, but this is making him doubt his skills. I have 7 yrs no-belt M/A exp. but I was taught referencing real fighting. Any help will be GREAT! Thank YOU