Sprint workout for 7th/8th grade

I am a new track coach taking on the challenge of teaching middle schoolers the basics of this sport. However, I need some assistance in the area of some good workouts for this age group. What kinds of things are appropriate?:help:

The emphasis of any program at this age must be on general development, coordination, which leads to alternation frequency in the longer term. Specific endurance and runs beyond 150m should be avoided at this stage and the role of competition is for performance advancement/experience/fun only. Peaking is not possible as the physical response of children at this age fluctuates wildly due to the variability of growth patterns. Training should be kept moving or attention will be rapidly lost and should probably not exceed 60 to 70min for a total of two to three sessions per week.