Kathryn Anne Fisher, 20, pleaded guilty to theft at Mold Crown Court and was told she should be 'thoroughly ashamed' of herself.
Fisher was secretary at Pentre Broughton County Primary School near Wrexham – a position of trust, the court heard.
An audit showed discrepancies of £11,600 but Fisher was only charged with stealing £3,395 - the money which had been paid into her account.
Judge Nicolas Parry told her: "This was despicable behaviour, serious dishonesty, theft in breach of a high degree of trust." But he also believed she was 'truly remorseful' for her actions.
The thefts of money collected from children were carried out repeatedly over a nine month period in multiple transactions.
The judge said: "You would have known that your criminality was highly likely to have an impact upon children, the reputation of the school and upon the reputation of the staff.
"It is a sad state of affairs if a head teacher at the school cannot trust a member of its staff."
Fisher received an eight month youth custody sentence, suspended for 12 months, and was ordered to carry out 300 hours unpaid work.
The judge ordered compensation in full within three months.
He said a further claim by the school to pay for temporary cover while the defendant was suspended was properly made, but he would not order that be paid because of her lack of means.
Sarah Morgan, prosecuting, said that Fisher, of Pentre Broughton, admitted 18 charges of theft amounting to £3,395 during a nine month period from Black Lane primary.
She was appointed secretary and administrator responsible for money collected, and would enter it on daily spreadsheets ready to be banked by the head.
When the school became aware that sheets had been filled in incorrectly, an audit was undertaken and discrepancies of £11,600 was discovered.
Fisher had been charged with the money that had been paid into her bank.
Mark Davies, defending, said that Fisher had started to take money with the intention of repaying it.
She had been employed for a comparatively short period of time and the auditor's report showed that she had been able to take advantage of the fact that controls around banking and reconciliation were weak at the school.
If there had been a greater degree of supervision, the matter would not have gone on for so long and the amounts would have been less, it was claimed.
He said: "I am not for a second trying to blame other people for what she has done."