MLAs have unanimously called on Education Minister Peter Weir to introduce mandatory autism training for teachers and classroom assistants.
With one in 30 children now diagnosed with autism, the Assembly heard that their needs weren't being met by schools.
A motion by DUP MLA Pam Cameron asking Mr Weir to explore mandatory autism training for teaching staff was amended by Green MLA Rachel Woods instructing him to take concrete action.
Autism diagnosis has doubled in the past six years and Mrs Cameron said the lack of support for children was "becoming more and more evident".
Of 5,000 calls a year to the Autism NI helpline, the "vast majority" concerned education, she said.
Almost 80% of autistic children are in mainstream schools. Over one-third are on a reduced timetable, she said, while others are not receiving the comfort and support in the classroom they needed.
Mrs Cameron said: "Every autistic child becomes an autistic adult. We need to spend now to save later or risk many of our autistic adults ending up in mental health services.
"The UK's largest autism research charity, Autistica, recently reported that autistic adults are nine times more likely to die through suicide than the rest of the general population."
Mrs Cameron noted that just 16% of autistic adults were in full-time employment. She said that the Executive had a duty to create a more inclusive environment.
"Other parts of the UK have already implemented mandatory autism training for teachers and Northern Ireland needs to follow suit or risk being left behind," she said.
Allowing a pupil with a hidden disability to struggle academically or socially was no different than failing to provide a ramp for a child in a wheelchair, she added.
Sinn Fein, SDLP, Alliance, Ulster Unionist and Green MLAs spoke in favour of the motion as did People Before Profit's Gerry Carroll.
Alliance MLA Chris Lyttle read a letter from the parents of a child who said he had been "constantly punished for behaviour beyond his control" by teachers and "it could have been easier if people were trained, equipped and supported to respond".
Sinn Fein MLA Cathal Boylan said teachers must understand autism and be "trained in the techniques and strategies" needed to teach a child with the condition.
Ms Woods said teaching unions supported mandatory autism training. The Education Minister supported the motion and the amendment and welcomed the Assembly consensus.