They are among 60,000 workers who were excluded from occupational pension schemes because they worked part-time.
A European court case in 1994 ruled that pension plans must be open to all workers but under British law, claims can be backdated for only two years and they must be made within six months of the end of the employment contract.
The NationalUnion of Teachers and five other unions went to the European Court of Justice to challenge the time limits.
The court overturned the two-year limit but referred the question of claims being made within six months to the House of Lords. It was due to make a decision at the time of going to press.
A teacher with 25 years' service who worked part-time for 12 years, retiring on a salary of pound;24,000, could benefit by an extra pound;1,800 pension and pound;5,400 lump sum.