In physical science learning, we have only to judge of what the teacher says and take that up. The teacher may be of any character; he can still teach you any physical science. For the knowledge that the physical science require is simply intellectual and depends on intellectual strength. The teacher can have in such a case a gigantic intellectual power without the least development of his soul.
But to learn spiritual science ( Vedanta, Upanishad, Bhagvad Gita,Tantra, Jyothish, Vasstu, etc) the personality of a teacher is important . The teacher should have pure spiritual light in his/her soul. It does not depend on how much knowledge teacher has in spiritual sciences and philosophies