Here's how the question of use by students under age 13 is answered on page 7 of the Adobe Spark Edu Guide:
Adobe Spark requires an account and login. Logins are used to sync content across devices as well as to backup content to our cloud storage. Children under the age of 13 are not allowed to create their own Adobe ID and so they will need to sign in with an account created by and supervised by a teacher or parent. Sign in with social media accounts is also supported.