Richard - you wrote me - 'Tac, my name is Richard Finlayson and in reading various postings it sounds like you are both an Aster and knowledgable about British mainline practice.
Sir, what I know about British railway practice could easily be written on the full-stop at the end of this sentence, but I'll try and help you.
'I...a train of about 8 Southern Railway freight cars.'
If you are going to get interested in British stuff, you have to start using the correct nomenclature - they are called wagons/waggons.
'So, to my question at last, were Schools ever used to haul freight?'
Nossir, as the bright and expensive paint scheme might have indicated, they were passenger locos all the way and VERY powerful high-steppers they were, too. Don't be misled by the teeny dimensions - the Schools Class locos were probably the most powerful 4-4-0 ever built for British rails. They were four-cylinder powerhouses and greyhounds of the rails.
'Also, what is a classic Southern Rallways freight engine that would be of the same general feeling of the LMS 9F of the G1MRA Project Loco fame?'
The Southern Railway, usually laid on pretty light profile trackage, did not have the larger locomotives in freight service [in English, goods service] like the Stanier 8F, but relied heavily on the like of the N1 moguls.
Sadly, the only G1 models I can find for this loco are in kit form, but a pal of mine says he will build you one in live-steam for around $7-8000 if you can wait a couple of years.
This website will give you a good idea of what was there during the dying days of steam, including the odd-looking but very successful Q1 Class 0-6-0 Austerity locomotive that looked as though it had left the shops before they could finish it.
This link might help you to get some idea of the Southern Railways steam locos - http://www.maunsell.org.uk/virtual shed/541/541_profile.htm
The U Class and older-style Q Class lasted until the end of steam, BTW. Both can be modelled in live steam G1 by the likes of Barratt Engineering, or by re-styling the Project model.
There are, of course, more G1 live steam and electrically-driven locos than Aster built, even though they produced the beautiful 'King Arthur' ten-wheeler. All the rebuilt BoB, WC and MN locos are there to be built in G1, in both 1/32nd or 10mm. All you need is patience if you are waiting for one to be built for you, or more patience and some degree of skill if you are going to build your own from the numerous kits available here in yUK.
My fave end-of-era Southern Region loco would have to be one of the mighty rebuilt Merchant Navy Class pacifics...even an American used to BIG stuff would be impressed with one of those.
Hope this helps, even if not much. I'm sure there are some real experts out there to give you some REAL input
tac the Griper