Al-jawab billahi at-taufeeq (the answer with Allah\'s guidance)
1) The Zahiri school of Islam (lit. submission, referring to the submission of God) is summed up by its own meaning. Az-Zahir literally means, "the apparent," or "literal sense." The Zahirists, thus, use the literal sense when interpreting religious texts and do not seek hidden or inward interpolation. Followers of the school are zahiriyah. This school is said to be founded by Dawud az-Zahiri.
Many of the scholars have labeled the Zahiri school extinct. It is more likely that the school never became established by a name but only the idea.
This school doesn't exist in the present day, the Zahiri methodology is said to be the root of the present day Salafi movement.
2) It is highly unlikely that it was permissible according to them to beat up one's parents as they used the Zaahiri (literal) meanings of the Qur'aan and Hadith.
The Zaahir (literal) of the Qur'aan prohibiting abuse to parents is expressly clear.
"And your Lord has decreed that you worship none but Him. And that you be dutiful to your parents. If one of them or both of them attain old age in your life, say not to them a word of disrespect, nor shout at them but address them in terms of honour. "
And lower unto them the wing of submission and humility through mercy, and say: "My Lord! Bestow on them Your Mercy as they did bring me up when I was young." (Al-Isra 17:23-24)
