At the primary level, it is better to teach in the mother tongue because

Mother tongue teaching at the primary level is best because it lets children learn in a natural atmosphere, as they already think and speak in it.

Instruction in the familiar home language removes the extra load of first decoding an unfamiliar tongue.

Developing self confidence is a genuine benefit but is one narrower outcome flowing from that natural ease.

Making learning easy is likewise only one aspect of the broader naturalness the mother tongue provides.

Helping intellectual development is again a partial gain, not the fullest single reason offered here.

This principle is stressed by NEP 2020, which favours the mother tongue as the medium in early schooling.