Did ash shafaee say imam layth bin saad is better imam than imam malik?
If imam layth bin saad is better than imam malik why don't we have laythi school of jurisprudence?
Imam Ash-Shaafi`i said:
"Al-Layth is more knowledgeable than Maalik."
(p. 524 of al-Shafi`i's Manaqib)
He means Maalik Ibn Anas, the Imaam of the people of Al-Madeenah.
And there was a Laythi school of jurisprudence.
The Laythi (Arabic: الليث) madhhab was an 8th-century religious law school of Fiqh within Sunni Islam whose Imam was Al-Layth ibn Sa'd.
And Allah knows best.
The complete statement of imam a-Shafi'i (see for example wafayat al-a'ayan of ibn Khallikan) is as quoted in the comment of @Kilise:
اللَّيْثُ أَفْقَهُ مِنْ مَالِكٍ إِلاَّ أَنَّ أَصْحَابَه لَمْ يَقُوْمُوا بِهِ
This might be translated as follows: "al-Laith was more knowledgable than Malik, but his student didn't compile or save his knowledge."
He has also been quoted saying in hilyat al-awliya':
الليث بن سعد أتبع للأثر من مالك بن أنس
which might be translated: "al-Laith is following athar (sunna etc.) more than Malik".
Others even made more stronger statements about the knowledge of al-Laith compared to Malik. However these statements must be considered in the correct context: What is the background of the person making the statement? What is the relation to both scholars? etc.
So basically a major reason why we don't know much about his madhab, is that instead of the students of Abu Hanifa, Malik, a-Shafi'i, al-Awza'i (whoms madhab vanished around the 3rd century) and Ahmad etc. the students of al-Laith didn't do enough efforts to keep the knowledge of their teacher and his opinions. And because of the fact that the major and most influential students of Malik were Egyptian (ibn Wahb, Abdurrahm ibn al-Qassim, Ashhab etc.) the madhab of a al-Laith already vanished and disappeared in his homeland at the time a-Shafi'i settled down there. But we still can read his ahadith in the sahih books, in al-Muwatta' of Malik and other hadith collections. Imam Malik used to call him "the person I trust" (or something similar) in al-Muwatta'.
But we know about the discussion or dispute between Malik and al-Laith (a correspondence) -both where students of ibn Shihab az-Zuhri and rabi'at ar-Ra'y- about Malik's opinion of considering the practice of people of Medina higher than ahaad and da'if ahadith. Imam a-Shafi'i also held the opinion of al-Laith saying that the sahaba were everywhere not only in Medina so their knowledge might be available with same "standards" in other places. Ibn Taymiyyah later somewhat confirmed the view of Malik (See in my source of Is it true that the Prophet Muhammad foretold the birth of Malik ibn Anas?).
Maybe imam a-Shafi'i said this because al-Laith did more efforts to collect knowledge by traveling, while Malik never left al-Hijaz because most reliable scholars lived there or came their for hajj. And the few ahadith Malik narrated from people of 'iraq are the less strong in his Muwatta'. And traveling to get knowledge was something imam a-Shafi'i considered as very important.
We also know that after moving to Egypt imam a-Shafi'i changed his madhab (his old madhab was more like the madhab of his teachers ibn 'Oyyanah, Waki'and Malik) and maybe he was influenced by the knowledge he gained from students of al-Laith.
An other point is that the scribe of al-Laith abullah ibn Salaah عبد الله بن صالح is considered as a da'if narrator by many authorities (like ibn Hebban, ibn 'Ady who said he makes unintended mistakes, the same was reported by ibn abi Hatim, while his father abu Hatim considers the weakness in his hadith -when he became older- to be due to ibn Najeeh -a companion of abu Salaah- who added fabrications in his books, a-Dhahabi pointed at the growing weakness with the age) .
The Arabic wikipedia site gives more information about the madhab of al-Laith which is similar to the one of a-Shafi'i when it comes to the osol. See also What are basic (osol al fiqh) differences & similarities between the 4 (existing) Legal Sunni Schools: Hanafi, Hanbali, Maliki, & Shafi'i? Charts?
As a comment on your comment about Bilal Philips statement: In no book of biographies like siyar a'laam an nubala' etc. you will find a-Shafi'i quoted as a student of al-Laith nor al-Laith quoted to have been thought a-Shafi'i, so this statement has no basis