For a student, of 6th going to 7th student, you can refer the ICSE science books or NCERT science books & prepare the student from it thoroughly. The previous year FIITJEE are available online, you can download and make the student practice from them. The examination tracks the strength of foundation developed by the student. So if the student have fundamentals clear, then clearing it will not be much of a problem.

For the sample paper you can consider the link below:

https://www.fiitjee.com/samplepaper.aspx

I hope this helps. Wish you a great eve!