Answer: Token economy
Explanation:
Token economy is defined as system in which tokens are used as reinforcers for systematic reinforcement of expected behavior.In this system, good behavior is rewarded with tokens or symbols that is exchanged with other desired reinforcers.
According to the question, Shay is using token economy by rewarding children with stickers whenever they perform bathroom habit correctly and then if any student receives tens sticker, he/she will be rewarded with a prize as exchange of desired token.