The sum you are sending to your son isn't taxable in your hands in India because you're paying.

These sums won't be taxable in India for your son too if you're gifting him.

However, the taxability of the money sent by you to your son in Australia for his education expenses will depend on the tax laws of Australia.

In general, if your son is a non-resident in Australia for tax purposes and he uses the money solely for education, it is unlikely to be taxable in his hands. But, if your son earns any income in Australia or receives any other type of income or allowances related to his education, such as scholarships or bursaries, then that income may be taxable in Australia as per their tax laws.

I recommend you to consult a tax professional in Australia to understand the tax implications of the money sent by you for your son's education expenses, as the tax laws may vary based on the specific circumstances of your son's case.

It is important to note that if you are sending a large amount of money to your son's bank account in Australia, you may need to comply with the requirements of the Reserve Bank of India (RBI) for remittances under the Liberalised Remittance Scheme (LRS).

Under the LRS, an individual can remit up to USD 250,000 per financial year for various purposes, including education. However, any amount over and above this limit will require prior permission from the RBI.