Discrete User Schema Permissions

Hi all,
I am trying to establish a "sandbox" database for a group of users/developers whereby each user has their own schema and complete control over their schema and only their schema.

I began by creating user logins (Windows Authentication), created schemas for each user where the corresponding login is the owner, and set the schema as default for the user.

At this point, the logins only had "public" and could not create tables. I then granted the Create Table privilege which allowed them to create a table in their schema. However, they could also create tables anywhere else in the database including another user's schema.
How can I set up an enironment where each user has control over just their schema? What permissions would I need to grant and at what level (database,schema, etc.). I also need them to be able to grant privileges on their own schema and/or schema objects.
Any help would be greatly appreciated.