one thing we do with eeZeeTrip (see Penfold's post) is to allow parents to manage their own phone numbers (we have emergency and secondary numbers). So, for example, if one parent is away on business they can easily swap to another emergency phone number. Phone numbers entered by parents 'trump' those coming form the MIS - if a school manually updates a number in eeZeeTrip we display a prompt saying that the number has already been validated by a parent.
Plus parents have to register with a valid email address (if this changes we catch NDNs).
