[TYPO3] restricted db mount secure enough?

[Felix Natter]

hi,

on a website with two main (be-)user groups (students and teachers), I have
put both in a "Editor" group for simplicity, but the students group only
has a DB mount on the student pages (part of the page tree).

Does that DB mount alone provide security such that students cannot access
pages outside their db mount or do I have to create two different groups
and assign restrictive page permissions (currently all pages are
group=Editor)?

thanks!

-- 
Felix Natter