Qiāoqiāobǎn yí shàng yí xià, liǎng gè háizi xiào de hěn kāixīn.
The seesaw goes up and down, and both children are laughing happily.
Tips
memory
跷 means to raise or tiptoe - like lifting your heels. The repeated 跷跷 mimics the bouncing up-and-down motion of a seesaw, with 板 meaning board or plank.