Underpowered networks / network servers in a school could increase this, if the computer was configured to load resources from the network at boot.
https://youtu.be/5M6OIOIND-0?t=1284 (this is an A5000, but the startup time is similar).
Applications that were not on the rom were loaded from the network which meant if all the kids loaded differnt things all at the same time the network/fileserver could get congested witch slowed loading times but I don't recall loading times being too bad but that might just be recalling the experiance though rose tinted glasses.
This allowed finer control of the applications what could be installed as the network was kept in read only mode for most of the time and only swapped into write enabled mode when updates and new applications were needed to be installed. the Read Only/Write Enable switch was a keyswitch on the fileserver case which was stored in a locked room. For the age it was "enough" security.
I have fond memories of the Archimedes as the first time I got paid for my code it was written on one.
Usually the schools has MDFS filers from BBC days being repurposed as econet servers which could barely cope with the load of a room full of machines coming up.
The IBM compatibles that seemed to replace them from RM were complete dogshit. Fortunately they killed that half way through the rollout when my sister was at school and went full netware instead.
I’m feeling old now.
My secondary school was entirely Acorn and we'd had Amigas, Acorns and then Macs at home. I'd never really encountered Wintel until Sixth Form, where the college was full of Windows 3.1-era RMs.
Couldn't believe how primitive they were - compared to Workbench and RiscOS it was like stepping back into some terrible technological past. Don't think I used them willingly once in the whole time I was there. Still never used Windows much.
I'm almost certainly remembering this wrong, but I believe these machines supported EcoNET with 10 base-T ethernet being available later with an addon podule. At my high school we did network authentication to log on and then also had access to our private folder which was also a network share, as well as some of the applications / boot scripts being on a network drive. The 3020's were surprisingly slow if you used the TCP/IP stack. I have fond memories of waiting for someone to start a game (Aarknoid iirc) and then sending flood pings to their IP causing the system to slow down to about 2fps. Fun times. I don't remember this being a problem on the A4000 or any of the RISC-PC range.
If you're based in the UK and need an Acorn nostalgia hit, then the Wakefield Acorn Users Group still has monthly meetings.
I also have very vivid memories of getting an x86 addon card (probably a 486) for one of our early RISC machines and being able to run Windows 95 within a window from the Acorn desktop; mind blowing in the late 90's.
TLDR: I remember the 3020 booting quickly, but the network services were slooooow.