Hello Jayati,

Some of the popular and top rated summer schools for high school in India are,

Symbiosis Summer School (Pune),  Fee: Rs, 120,000 including food and accommodation

Summer Immersion Program at Flame University (Pune), Fee: Rs, 40,000

Doon School’s Summer Programme on Leadership (Dehradun), Fee: Rs 140,000

Summer Programmes at UWC Mahindra College (Spread across India majorly in rural and semi-rural areas), Fee: Rs 31,000 to Rs 193,000 depending on the course and the module.

 India Summer School by King’s College London (New Delhi, Mumbai, Berlin, London), Fee: Rs 45,000

Hope this helps!