Hanafi
The sources give no view for it here.
صوم يوم الشك
هل يصح صوم يوم الشك على كل وجه؟
Each school’s answer
In our wordsHanafi
Not stated in the sources
Maliki
Not stated in the sources
Shafi'i
Not stated in the sources
Hanbali
Not stated in the sources
The texts
مسألة: ذهب بعضهم إلى أنه لا يصح صوم يوم الشك على كل وجه وهذا غلط؛ لأنه يوم محكوم له بأنه من شعبان كما قبله، واعتبارا به إذا كانت السماء مصحية. [أحكام في رؤية الهلال]
«الإشراف», al-Qadi Abd al-Wahhab p. 426
From the schools’ own books
Maliki
The sources give no view for it here.
Shafi'i
The sources give no view for it here.
Hanbali
The sources give no view for it here.
What is «in our words» is our standard wording; the books’ texts stay as they are.