Department for Education census figures show there are 5,179 pupils attending 28 private schools in the county accounting for 12 per cent of pupils which is among highest proportions in the West Midlands region.
Now the opposition has pledged to end the "tax privileges enjoyed by private schools", after members voted at its annual conference to absorb all pupils and wealth from the sector into the state system.
But the Independent Schools' Council said a move to abolish private schools would constitute "an attack on the rights and freedoms of parents to make choices over the education of their children". It added that Labour's decision was "an ideological distraction" from dealing with the real problems faced by state schools.
Private School Policy Reform, a new independent think tank, published a report last month with options for change.
Its ideas ranged from scrapping private schools’ charitable status and charging tax on student fees, to nationalisation.
Independent Schools' Council chief executive Julie Robinson said: "Every family with school-aged children would be affected if independent schools were abolished.
"State school class sizes would swell further, resources would be stretched and the financial strain on already-stretched budgets would be enormous."
Almost one in five primary school kids and 12 per cent of secondary school pupils in Shropshire are taught in classes that are too large – those with more than 30 pupils.
Some classes have even swollen to 36 or more – 369 primary and 78 secondary pupils are in classes of this size.
Shadow education secretary Labour's Angela Rayner said: "Boris Johnson has broken his promise to tackle the tax privileges enjoyed by private schools.The next Labour government will immediately close those tax loopholes and use that money to improve the lives of all children.
"Our Social Justice Commission will look at how private schools can best be integrated into the education system to make it fairer for all children, regardless of their background.”
Across England's state schools, the number of pupils in large classes has increased in recent years.
In January, 11 per cent of primary school children were in classes with over 30 pupils – up from 10 per cent a decade ago.
For secondary schools, the figure is nine per cent up from seven per cent in 2009.
A Department for Education spokeswoman said: “The UK boasts a diverse education system, in which state schools, independent schools and universities are encouraged to share their expertise and resources through our partnerships programme.
“The gap between state funded schools and independent schools has never been smaller – 85 per cent of state funded schools are now rated good or outstanding compared to 68 per cent in 2010."