There are not roles and permissions like there are in other products.  based on the functional requirements of your site, you could code this type of functionality in.   You could assign types/subtypes to the entities and then use this value to determine the type of processing that is allowed.  

I went to the Elgg conference in Boston last week and this topic came up.  They would like to put in more hooks so that developers can more easily build these types of systems based on their own needs.

So it's possible with a lot of work? Might be easier just to make all teachers admins? But that would result in chaos I am sure! :-)

If we can make it compliant with the UK secondary school educational requirements I am sure it would boost the user base greatly. Espacially if there was a way to do this, essentially they need greater control over who can see what and edit what.

How would I set about doing what you have suggested? I am a graphic designer so UI and front end is what I am trained for, but I am trying to get to grips with MySQL and PHP now.

At the moment the govt want the schools to use Fronter which is a little heavy duty for what the schools need to acheive....

@DLRP
I am not too familiar w/ (UK) BECTA, but will google and learn.
I am located in the USA, 
My interest in this BECTA ?
Projects in UK related to school websites !
We do have Admin, Teacher, Student  User levels...
Feel welcome to send me private message if you'd like discuss more and exchange info, ideas, etc

@dlrp
I wonder if there's a way to meet your requirement for  "three levels of access, Admin, Teacher and Pupil, each with the ability to do different things (edit areas etc.)" without having to extend Elgg at all.

Would you consider using Groups as the way to control who sees what?  Let there be a set of groups for Admins only, a set for Teachers only, a set for Pupils only,  and whatever combinations you'd need. With by-invitation groups, group owners would decide who gets in a group.

Admittedly, it could get to be quite a bit of administrative work for group owners, but it would keep people from seeing and/or modifying things they shouldn't be.

And I guess it might be a problem that students could form their own groups and keep people out. That might worry adults, who wouldn't be able to monitor what's going on in the groups.