Peter Bradley, deputy director of the childrenâs charity Kidscape, said: âChildren who have been sexually abused would be horrified to read this judges remarks.
âSchools are not places where those attracted to children can work â schools are there to provide learning in a safe environment where children know the people who look after them can be trusted and relied upon.
âThis teacher should not have been in the profession and it is outrageous for the judge to say many teachers are sexually attracted to children.
âThe message needs to be clear â if you are sexually attracted to children then you don't work with them.â
Christine Blower, General Secretary of the National Union of Teachers, said: âTeachers are professionals whose interest is ensuring children and young people achieve their educational potential.
âTo suggest their interest in pupils could understandably be anything else is totally unacceptable.â
Jayne Phillips, Senior Legal Advocate at the Association of Teachers and Lecturers, added: âIt is a very worrying message to send out.
âThe judgeâs comments do not reflect our knowledge of the UKâs teaching staff â they would be appalled by the suggestion that they are in anyway attracted to children.â
Married Armstrong was caught after a colleague at the Little Heath School in Tilehurst, near Reading, Berks, reported him to police.
Reading Crown Court was told that the teaching assistant became alarmed after noticing files on Armstrongâs laptop with names including ârape wifeâ, ânude modelâ and âgay alligatorâ,
Police arrested Armstrong and found 4,500 indecent images and videos on two laptops and an external hard drive. More than 300 of the images were in the two most serious categories, some involving children as young as two.
He admitted five charges of making indecent photographs or pseudo-photographs of children between 2007 and 2010. The court heard that some of the images were not of real children but Japanese cartoons depicting youngsters in sexual scenes.
Judge Mowat handed Armstrong a 12-month prison sentence, suspended for two years.
She added: âThis was by any standards a substantial collection, with some 300 of the worst kind.â
Armstrong, of Devizes, Wilts, was placed on the Sex Offendersâ Register for ten years and served with a sexual prevention order banning him from owning a computer or device capable of connecting to the internet.
He was also ordered to undergo treatment for his attraction to children and is automatically banned from working with youngsters.
Robin Shellard, defending, said his client had worked at many schools and colleges during his career and had an impeccable record.
The case is not the first time Judge Mowat has stirred controversy over sentences handed to sexual offenders.
In 2008, she allowed former headmaster Phillip Carmichael to walk free from court after accepting that medication for Parkinsonâs disease had turned him into a paedophile.
Sentencing a bus driver to ten-months in jail in 2006 for abusing a 12-year-old girl, the judge acknowledged that she felt âobligedâ to lock him up because of âcurrent views about sentencesâ.
âI have a record of trying to suspend sentences in cases like this and them ending up in the Court of Appeal,â she told Robert Prout, following a public outcry over the brevity of prison sentences for sex offenders.