The axing of all funding for support staff training will make schools "less efficient and effective", Government critics have said.
Heads and local authorities will no longer be given any money to pay for employees to become high level assistants or to attend courses.
The #163;25 million cuts have been made by the Training and Development Agency for Schools (TDA), which was told by the new government to cut spending by #163;30 million this year.
Unions say the cuts will deprive schools of qualified support staff, putting workforce reforms for teachers in jeopardy. Their numbers boomed after teachers were freed from having to do peripheral tasks in the classroom such as hanging displays and photocopying.
Higher level teaching assistants (HLTA) can cover classes on their own for short periods.
In 2009 TDA officials gave local authorities #163;65.7 million in total. This included funding for the teaching assistant training and "golden hello" grants to attract graduates to sign up to teach shortage subjects. These bonuses, which cost around #163;25 million a year, will still be paid in 201011.
The TDA said local authorities and schools that wanted to continue training teaching assistants would have to pay for it themselves.
But Christina McAnea, head of education at the union Unison, said: "The Government is playing fast and loose with children's educational needs. What schools desperately need are more teaching assistants trained to HLTA level. Now they are being told there is no money available."
Mary Bousted, general secretary of the Association of Teachers and Lecturers, called the cuts "frightening". She added: "The new Government doesn't seem to realise that a little knowledge is a dangerous thing, they don't seem to understand how schools work in the 21st century. It's a mistake to have such a huge resource as teaching assistants and not to train them."
A spokeswoman for the TDA said: "Where financially viable, we will continue to support funding for HLTA assessments for those candidates currently registered for assessment."