Elizabeth Smart was thrown to the ground, was scratched, hit, had clumps of her hair pulled out and was left bleeding by a relative of another mum, Sharon Nyberg, 43.
A court heard that before the assault Ms Smart and Nyberg had had a foul-mouthed row.
Ms Smart was offered refuge in the school, but when she left Nyberg was waiting for her outside the school gates.
Nyberg barged another parent holding a toddler out of the way then attacked Ms Smart. During the attack at St Michael's Church of England First School, in Alnwick, another parent, Jolene Angus, 26, also joined in with the attack.
John Cleasby, prosecuting, said: "This was in broad daylight outside a school with small children in the vicinity. It was witnessed by a number of teaching assistants, who were sent out in order to bring the violence to a conclusion.
"In due course the assault stopped and Nyberg and Angus readjusted their hair and left the scene calmly."
After the incident, Angus and Carlene Balmbra, 28, set up fake Facebook accounts in the names of two witnesses in an effort to scupper the case.
They printed off made-up conversations between the women which appeared to undermine the case and sent them to the Crown Prosecution Service and the school.
But their lies were exposed, and now Nyberg and Angus have admitted affray and Angus and Carlene Balmbra admitted attempting to pervert the course of justice.
The court heard the incident outside the school happened on June 27, 2011. Ms Smart had become involved in an angry exchange with a member of Nyberg's family and feelings were running high.
The school secretary came out and offered Ms Smart refuge.
Mr Cleasby said: "She thought she would be fine going home with friends and had been offered a lift.
"While exiting the school premises she became aware that Sharon Nyberg had waited for her.
"She came directly at her and it was clear she was intent on violence from the outset.
"She barged one lady out of the way who had a two-year-old child in her hands."
Nyberg admitted affray and was given a 12 month community order with 60 hours of unpaid work.
Angus pleaded guilty to affray and perverting the course of justice and was given six months prison suspended for 12 months with 100 hours of unpaid work.
Mother-of-three Balmbra admitted perverting the course of justice and was given a 12-month community order.
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