Scorwriters which have some sequencing capabilities. The main software available is Passport Encore, and its cut down version Passport Musictime, Coda Finale, and Sibelius, which was previously only available on the Acorn but is not out for the PC and Mac. There are other, cheaper versions around, of which I've had a detailed look at Music Works by Middle Earth software. Coda Finale has an excellent output but is a little difficult to use at first, so many people get put off it soon. If you persevere, however it is worth it.
Younger pupils find it very difficult to use and many lack the patience to get it working properly.
Passport, I understand have gone out of business, so I don't know if you can get the software any more. Their software is outstanding and very simple to use. You can get excellent results very quickly and the young pupils get on with it very well. Encore can produce up to 64 staves but Musictime only 16. Individual part extraction is available on Encore but not Musictime.