In order to apply as a TA with LAUSD, you need to take one or two tests:
If you have completed less than 48 units in college, then you'll need to complete BOTH the Instructional Assistance Test AND the District Proficiency Test.
If 48 units or more, then you just need to take the District Proficiency Test.
To prepare for the test, read these PDFs:
Instructional Assistance Test (info coming soon)
If you don't pass, you need to wait 30 days until the next test and pay $7 again. (In case you need it, the official LAUSD page is here.)
To sign up for the test, you follow a crazy procedure:
Create an account on this LAUSD job search site – this is SEPARATE from the account you create for actually applying for the TA position. It's crazy, but that's how it works.
Find 'job posting' DP&IA-11-21-XA1 District Proficiency and Instructional Assistance Assessment.
Click the Apply button.
Answer the questions and then select "Submit Application" -- this is your 'application' to take the test. You'll still need to pass the test and then submit your teaching assistance application.
It costs $7 and save your receipts so that we can reimburse you!
(In case you need it, the official LAUSD page describing the application process is here)