Parents may expect their children to have tailormade study plans as a result of government spin on personalised learning, the NASUWT warned this week.
Chris Keates, the union's general secretary, said some schools believed teachers had to produce individual lesson plans for each pupil. Teachers need to be protected from this expectation, she said.
She called for the review of personalised learning to give a clear definition of the term, making clear what pupils, parents and teachers can expect. The review is headed by Christine Gilbert, who is due to report before she takes over as chief inspector next month.
Ms Keates said: "An agreed definition needs to be reached on what personalisation means in practice. It is important to ensure there are no unrealistic expectations of what schools will be able to deliver.
"Signs are already emerging that some schools are interpreting personalisation as meaning teachers must prepare individual lessons for each child they teach. This is unnecessary and inappropriate, and Christine Gilbert has been right to recognise this fact.
"The review's outcomes must recognise that for most pupils personalisation cannot mean significant educational experience outside a whole class context."
The NASUWT's submission to the inquiry contains 36 recommendations about how personalised learning should be translated from rhetoric to reality.
It emphasises the importance of special schools in delivering support for children with special educational needs and warns against overloading teachers with bureaucratic tasks.
If it is to gain teachers' support, personalised learning must be a way of building on existing success and not portrayed as a response to a crisis of underachievement, the union said.
Changes are needed to the way Ofsted inspects schools in order to give them the confidence to experiment with new approaches.
The current system focuses too much on how schools do things and not enough on pupils' results, it said.