Ruling on students standing up to greet the teacher when he enters the classroom
Question

                It is customary for the students to stand up out of respect for the teacher when he enters the classroom. Is that permissible?.
Praise be to Allah.
    Al-Tirmidhi (2754) narrated that Anas (may Allaah be pleased 
    with him) said: “No person was dearer to them than the Messenger of Allaah 
     (peace and blessings of Allaah be upon him). When they saw him, they 
    did not stand up, because they knew that he disliked that.” Classed as 
    saheeh by al-Albaani in Saheeh al-Tirmidhi. 

    The Prophet  (peace and blessings of Allaah be upon him) 
    disliked them to stand up for him, out of humility towards his Lord, and so 
    as to differ from the custom of the arrogant and tyrants. Tuhfat 
    al-Ahwadhi. 

    The scholars of the Standing Committee for Issuing Fatwas 
    were asked: What is the Islamic ruling on students standing up for their 
    teachers when they enter the classroom? Is it permissible or not? 

    They replied: 

    The best of guidance is the guidance of Muhammad  (peace 
    and blessings of Allaah be upon him) and the worst of matters are those 
    which are innovated. The best of generations is that to whom the Messenger 
     (peace and blessings of Allaah be upon him) came, and the generations 
    who came after him, as is proven from him  (peace and blessings of 
    Allaah be upon him). His practice with his companions with regard to this 
    matter was that when he came to them, they did not stand up for him, because 
    they knew that he disliked that. So this teacher should not tell his 
    students to stand up for him, and they should not obey him if he tells them 
    to do that, because there is no obedience to any created being if it 
    involves disobedience towards the Creator. 

    And Allaah is the Source of strength. May Allaah send 
    blessings and peace upon our Prophet Muhammad and his family and companions. 
    End quote. 

    Fataawa al-Lajnah al-Daa’imah 
    (1/172). 

    And Allaah knows best.