[DeltaMustang65]

I couldn't even find the answer to this in my old mustang shop manuals, so I went to the trusty college engine rebuilding shop book. This is what it says:

To replace a freeze plug, use the following procedure:

1. Drive a drift or large full-shank screwdriver through the plug.

2. Pry sideways, without scraping the engine block or cylinder head. The plug should pop out.

Here's what I'm guessing you want...

3. Sand the core plug hole in the engine and wipe it clean.

4. Coat the plug hole with non-hardening sealer. <=====

5. Drive a new freeze plug squarely into position.

Unless you're using an expansion freeze plug or some other weird type of plug, I'd say your teacher is wrong on this one.