http://www.instructables.com/id/Lego-Ev3-Build-for-Learning-Programing-and-Robotic/

https://github.com/petrukhnov/ardugame

Suitable for 12+ years old kids in classroom.

arduino reward box

Combining arduino and lego is great for inspiring people, and especially kids. Arduino components are cheap, used lego is cheap.

Example of combining servo and arduino without any glue, or parts modifications: https://www.instructables.com/id/Servo-SG90-With-Unmodified-Lego https://www.instructables.com/id/Servo-SG90-With-Unmodified-Lego-V2/

DC motor inside lego:

Brick 1 x 1 (3005/3062/6541) x 5

Plate 1 x 1 (3024/4073/85861/33291)

Propeller 3 Blade 3 Diameter (6041)

Technic, Axle 4 (3705)

Technic, Axle 6 (3706) x 2

Technic, Axle and Pin Connector (3651) x 2

Technic, Brick 1 x 4 with Holes (3701) x 12

Technic, Brick 1 x 6 with Holes (3894) x 4

Technic, Bush (3713) x2

Technic, Pin (2780/4459/3673) x 8

Technic, Plate 2 x 4 (3709b)

Other alternative is to 3d print case:

https://github.com/LEGO-compatible-gadgets/PELA-parametric-blocks