In general, NCERT books/course books prescribed by the CBSE/ICSE/STATE BOARDS may be referred to for preparation. We also have following books/materials for OGO preparation:
OGO Workbooks–English, Mathematics, Science, Cyber, (For Classes 1 to 10); Hindi (for Classes 3 to 10)
OGO NLE Books– English, Mathematics, Science & Cyber(For Classes 1 to 10).