Dear Sir,
Hope you are doing well !!
Either you can show it as an income from other sources or PGBP.
If the coaching receipts are substantial and there are separate expenses like staffing, coaching premises rentals, computers, etc, then it shall be appropriate to show it under PGBP.
On the contrary if the scale is small and there no substantial expenses relating to that, offer it as income from other sources.
You can also take the benefit of section 44AD subject to litigation.