Image copyright Google Maps Image caption Parents at the Glen Park school were outraged over the situation

A San Francisco teacher on extended sick leave due to breast cancer has had to pay for her own substitute, sparking a nationwide outcry over the policy.

The average cost for a substitute in the city is $200 (£150) per day, which gets deducted from the sick teacher's salary, thanks to a 1976 state law.

Parents have responded by raising over $13,000 to help the teacher pay her medical bills, local media report.

Lawmakers and the city teacher's union are now considering changing the rule.

The Glen Park primary school teacher battling cancer has asked not to be named to protect her privacy.

Local parents were shocked to learn of the law when the well-loved teacher fell ill.

"Parents were outraged and incredulous - like, this can't be, there must be some mistake," Amanda Fried, whose children go to the Glen Park School, told the San Francisco Chronicle.

Ms Fried added that the school's other teachers were unsurprised by the situation.

"That makes it even more sad, because teachers expected to be treated poorly."

Media playback is unsupported on your device Media caption "I have 29 textbooks for 87 pupils": Why these teachers in Oklahoma are striking

In San Francisco, where the cost of living is notoriously high, teachers make around $82,000 annually, US media report.

They receive 10 days of paid medical leave from the school district. If they require extended medical leave, they are entitled to up to 100 days - but must foot the cost for their own substitute during that time as California teachers are not a part of the state's disability programme.

The city teacher's union may now raise this issue during 2020 negotiations.

United Educators of San Francisco President Susan Solomon said in a statement that the group looked forward "to making improvements in this and other parts of the contract" between teachers and the school district.

The teacher's story has been covered by many national news outlets and sparked discussions across social media. In the wake of this nationwide scrutiny, state lawmakers have also been made aware of the controversial law.

State Senator Connie Leyva told NBC News : "I think that times have changed and it's our job to change with the times."

Earlier this year, teachers in Los Angeles went on strike to demand more support staff, smaller class sizes and better pay. Teachers in Colorado were also striking this year for better compensation.

Last year, a wave of educator strikes swept the nation, with thousands of teachers protesting unfair pay. In West Virginia, teachers specifically highlighted issues around rising healthcare costs.

Media playback is unsupported on your device Media caption 'The resources have been dwindling, the staffing has been dwindling, students are suffering'

On the GoFundMe page parents started last month to pay for the San Francisco teacher's medical care, substitute and lost income, she was described as a "true professional" who loved her students, US media reported.

"Just a few days after her surgery, she took the time to write out 22 completely personalised notes to the students in the class thanking them for their support, telling them she missed them dearly and encouraging them to continue working hard," the fundraisers said.

The campaign closed after surpassing the initial goal of $10,000.

"My family and I are truly grateful for this gift," the teacher wrote. "My heart is lifted and it gives me so much strength to know that so many people care about me and my family."