Multi tenancy by schema - Deny access to another tenants
The solution is to add the Grant permissions and do not add any read or write role to the user.

GRANT SELECT ON SCHEMA::[SCHEMA] TO [USER]

GRANT INSERT ON SCHEMA::[SCHEMA] TO [USER]

GRANT UPDATE ON SCHEMA::[SCHEMA] TO [USER]

GRANT DELETE ON SCHEMA::[SCHEMA] TO [USER]