SQL Server: hierarchy of permissions for schema?
Quick answer: For developers, you can GRANT CONTROL on that schema.

Background:


To see what can be GRANTed: GRANT Schema Permissions
To see what each permission means: Permissions Naming Conventions 


The intersection of these two give the schema permission meanings:


CONTROL implies the rest and is the highest permissions of any securable
SELECT, DELETE, INSERT, UPDATE is DML on objects in that schema
EXECUTE to run scalar UDFs and Stored Procedures in that schema
ALTER, REFERENCES is DDL (CREATE, ALTER, DROP) on objects in that schema
VIEW DEFINITION lets folk see the code and definitions


Except for CONTROL, these are mostly orthogonal to each other: folk can EXECUTE code or SELECT, from a view but not see the definition (VIEW DEFINITION) of these.

You also have the database and server permissions which are implied higher up then CONTROL on schemas: see Permissions Hierarchy