Most motherboards come with sound anyway, so that is a bonus

I don't think FireWire is too important, and if you buy a device that needs FireWire (like a FW hard drive) it may come with a PCI FireWire card included, so maybe you should wait until you need it and get a PCI FW card then.
I have three motherboards of my own. One of them is the Asus A7V333-RAID, which uses the VIA KT333 chipset, and it has onboard USB 2.0 and FireWire, onboard sound, but no onboard video. I tried to update the BIOS and it failed, so now it is on the way back to Asus for repair

The non-RAID version doesn't have FireWire. The A7V333 will probably support AthlonXP's up to the 3000+, including the future ones that use 333MHz bus instead of today's 266MHz bus.
I also have an ECS K7S5A, which is a low-priced board that uses the SiS 735 motherboard chip (I would say "chipset," but they built it all into one chip with SiS 735). It has basic onboard sound and supports AthlonXP's up to at least the 2200+, probably up to the 2600+. It works fine, I'm using it now. It has no USB 2.0, FireWire or video, but the board is so cheap that I could add a PCI USB 2.0 card and a PCI FireWire card when I need them.
For my computer at work, I got an Asus A7N266-VM, which is a great microATX board using the nVidia nForce chipset. It has onboard GeForce2MX video, excellent Dolby-certified onboard audio, onboard network card, and supports up to an AthlonXP 2200+ at least, maybe more. I built some computers for my workplace using this one too. It would be great for school, with about 256Mb of RAM and Windows2000. It doesn't have USB 2.0 or FireWire, but you could add those with PCI cards if you needed them. It also has an AGP slot so you can upgrade to a separate video card later. I really like this motherboard a lot, and nForce2 should be even better when it comes (similar price, USB 2.0, FireWire, and support for the future AthlonXP's with 333MHz bus speed).
Another chipset that has onboard video is VIA's KM266 chipset, and I did see a KM266 motherboard which has USB 2.0,
optional onboard network, onboard 3D video, and onboard sound:
Biostar M7VIQ
To compare the prices of these different boards:
A7V333-RAID is $140
A7N266-VM is $80
K7S5A is $55
M7VIQ is $70
At work, we are using AthlonXP 1800+'s and they are very fast for doing office work, even with our antivirus software slowing them down.
Gigabyte had a problem with some of their Pentium4 boards about six months ago, and they didn't seem to fix it very well, so I'm not sure if they are doing good quality control and testing. I do like their board layouts on the 7VRX boards, it's perfect.