She is on leave through the end of the school year, the San Francisco Chronicle reported.
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Normally teachers get 10 sick days a year, but can take 100 days of medical leave. That leave comes at a cost directly from the regular teacher's paycheck, KGO reported.
A substitute's salary runs from $174.66 to $240.26 a day, the Chronicle reported.
The payments are required by state law, according to the Chronicle. That's because California teachers don't participate in the state's disability insurance program. Since 1976, teachers can have five months of leave due to illness or injury with full pay, minus the cost of the substitute.
The pay can even be deducted in cases where no substitute was hired, the Chronicle reported.
There is also a Catastrophic Sick Leave Bank that is comprised of donated days from other teachers. Ill educators can use up to 85 additional days after the other days are exhausted, and at no cost, KGO reported.
Friends and parents of the teachers had set up a GoFundMe campaign to help offset the cost of the substitute while the teacher receives treatments. The account recently stopped accepting donations, KGO reported.
Students at Glen Park also planned bake sales to help their teacher, the Chronicle reported.