I chose to explore Tynker because it is available as an app through our school district's "App Store" on my students' iPads. On an iPad, the app needs the iPad software to be IOS 11.4 or later. The age rating is 4+ but geared more towards ages 9-11. There are various subscription plans but price depends on if a school district is buying a license or if a parent is buying it. There is also a free version but that only has access to so much. Through a free teacher account, there is no limit on how many students can be in a class, but there are only 3 free courses that can be assigned to students. There is a way to add student accounts so if a class is 1:1, then students will have their own Tynker account.
https://www.tynker.com/
https://www.tynker.com/