Jenkins is on the money on this one.
Umpiring as an IC is is a slippery slope that has yet to be set in federal law with eight states having IC/Officiating laws, and six states having IC/Officiating "rulings":
http://www.naso.org/rprt/SpecReptIndCont.pdf
The NASO article also agrees with Jenkins and I, that someone umpiring for their employer means employee when umpiring.
A person working for a school district would be an employee/official if officiating at any school within the district.
There is no harm for the employer if they classify someone as "an employee for one item, an employee for all", and a huge risk if they try to play the employee sometimes, IC other times "game".
The following article discusses a school setting from another perspective.
Higher Markets’ Purchasing Pulse newsletter in September, 2000
http://www.rainassoc.com/employee.pdf
"Of over thirty cases in which the US Tax Court, US District Courts, the US Courts of Appeals and the US Supreme Court have issued opinions based upon Revenue Rule 87-41, there is not a single case where a taxpayer has successfully argued that a person can be an employee and a contractor concurrently for the same employer."
"And as if to add insult to injury, in some instances 26 USC 6672 gives the IRS authority to hold "responsible parties" liable for a penalty equal to 100% of the employment taxes not properly collected and paid for employees. A "responsible party" can include officers, managers and any other person who exercises a controlling decision in the process of whether or not to collect payroll taxes — and that means you and me folks. There’s no question that there is some degree of personal liability as a consequence of improperly classifying employees as independent contractors.
So here’s the denouement — if your institution is issuing an IRS Form 1099-MISC and a W-2 to the same name, you just might be announcing that you’re underpaying the tax man and you probably should prepare the welcome mat for the IRS auditors."