Done quite a few junior races not so many recently mind, however some of my favs where;
Three shires - FAST run out then a great climb
High Rigg - same as above, found it very tough every time, also organisation was top notch
Sedbergh old FRA - great courses all round
Then some of the BOFRA's
Kettlewell - love this race it think it has a bit of everything squeezed into a short race
Wasdale - Pritty unique and UNBELIEVABLY steep!
Troutbeck - A Kendal winter league race, used to love the variation and a great decent!
Other randoms now!
Ambleside sports and grasmere - Both good courses but id say its the sense of occasion thats makes the good also you normally get a good quality field.
And bear in mind for the over 16 juniors there is some great senior shorts you can do!
Haha thats quite a list brings back the good memories!