Some people say it is haram to stand in respect of scholars, teachers, parents etc...

Let us see hadiths which prove its permissibility

1) Narrated Abu Sa`id Al-Khudri:

The people of (Banu) Quraiza agreed to accept the verdict of Sa`d bin Mu`adh. So the Prophet (ﷺ) sent for Sa`d, and the latter came (riding) a donkey and when he approached the Mosque, the Prophet (ﷺ) said to the Ansar, "GET UP FOR YOUR CHIEF OR FOR THE BEST AMONG YOU" Then the Prophet (ﷺ) said (to Sa`d)." These (i.e. Banu Quraiza) have agreed to accept your verdict." Sa`d said, "Kill their (men) warriors and take their offspring as captives, "On that the Prophet (ﷺ) said, "You have judged according to Allah's Judgment," or said, "according to the King's judgment."

Bukhari # 4121

2) Narrated Aisha, Ummul Mu'minin:

I never saw anyone more like the Messenger of Allah (ﷺ) in respect of gravity, calm deportment, pleasant disposition - according to al-Hasan's version: in respect of talk and speech. Al-Hasan did not mention gravity, calm deportment, pleasant disposition - than Fatimah, may Allah honour her face. When she came to visit him (the Prophet) "HE GOT UP TO (WELCOME) HER", took her by the hand, kissed her and made her sit where he was sitting; and when he went to visit her, she got up to (welcome) him, took him by the hand, kissed him, and made him sit where she was sitting.

Abu Dawud # 5217. Hadith is Sahih. 

Regarding the narrations which prohibit standing up then they are only for one who likes it to happen for him/her out of pride. Or Prophet (Peace be upon him) did not like it for himself due to humility.