6th grade:
bicep
tricep
hamstring
quadricep
gastrocnemius
brachioradialis
anterior deltoid
posterior deltoid
abdominals
external obliques
trapezius
latissimus dorsi
erector spinae
gluteals
pectoralis
For 7th grade add:
soleus
achilles tendon
tibialis anterior
For 8th grade add:
hip flexor
adductor
abductor
sternocleidomastoid