Thanks to Ole Olsen for his help with this!

1. Existing Twitter users - add the hashtag #MOsoccer to any tweet
that offers final scores. That will offer a real-time feed for the
media, coaches and fans to see results throughout the state.

2. New Twitter users - before creating a Twitter account, consider
creating a new email address to administer the account so that it can
remain with the school when they move on.  It can become an
administrative email address for Twitter, a Facebook Page, any other
web services they may use to support their program. Once created, then
visit https://twitter.com/ to create an account.

There are many Twitter applications for smart phones.  Here is a link
for all apps - https://twitter.com/#!/download

I've been very happy with Hootsuite (free version) which also runs on
PC's.  One benefit is tweets can be scheduled so it's easy to add
notes for players and fans in advance that ensures they are sent out
at the required time. Best time to schedule? Consider your audience.
When will kids be on Twitter? Immediately after school and when they
are at home.  Same with parents.

For non-smartphone users, Twitter users can use Text Messaging (or
more specifically SMS).  Here's a link with information -
https://support.twitter.com/groups/34-apps-sms-and-mobile/topics/153-twitter-via-sms/articles/14589-getting-started-with-twitter-for-sms

A Twitter account is not needed with the new "Fast Follow" program -
http://blog.twitter.com/2010/08/introducing-fast-follow-and-other-sms.html

Note that SMS/text messaging prices apply on your mobile account.