The occupational duty of a brahmana should not be accepted by persons in lower social orders.

The occupational duty of a brahmana should not be accepted by persons in lower social orders, especially vaisyas and sudras. For example, an occupational duty of the brahmana is to teach Vedic knowledge, but unless there is an emergency, this professional duty should not be accepted by the ksatriyas, vaisyas or sudras. Even a ksatriya cannot accept the duties of a brahmana unless there is an emergency, and then even if he does so he should not accept charity from anyone else. Sometimes brahmanas protest against Krishna consciousness movement for creating brahmanas from Europeans, or, in other words, from mlecchas and yavanas. This movement, however, is here supported in Srimad- Bhagavatam. At the present moment, society is in a chaotic condition, and everyone has given up the cultivation of spiritual life, which is especially meant for the brahmanas. Because spiritual culture has been stopped all over the world, there is now an emergency, and therefore it is now time to train those who are considered lower and condemned, so that they may become brahmanas and take up the work of spiritual progress. The spiritual progress of human society has been stopped, and this should be considered an emergency.

Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Seventh Canto, Chapter 11 – Text 17