I think, there is not a general definition of necessary and sufficient  
conditions of a school in science. 
 
Szaki (1981:18-25) wrote about four meanings of the school concept: 
 
- an institutional meaning: Members of a school articulate in an  
institutional arrangement; 
- a psychological meaning: Members of a school articulate the same theory= 
; 
- a typological meaning: Theoreticans of science define a group of  
scientists as a school if they have the same method; 
- a national meaning: Members of a school work at the same place. 
 
Sometimes there are more conditions for the definition of a school in  
the literature. The following definitions are from Lindenlaub (1993:406)  
and Rieter (2002:145): 
 
- one or more standard publications; 
- a written agenda of the school; 
- journals or other publications from the school; 
- a scientific association; 
- many pupils; 
- a chief schoolmaster. 
 
In an other definition by Pearson (1999:557) a school practices kuhnian  
'normal science'. 
 
Literature: 
 
Lindenlaub, David F. (1993): The Myth of the Older Historical School of  
Economics, in: Central European History 26, pp. 405-416. 
 
Pearson, Heath (1999): Was There Really a German Historical School of  
Economics?, in: History of Political Economy 31, pp. 547-562. 
 
Rieter, Heinz (2002): Historische Schulen, in: Issing, Otmar (ed.):  
Geschichte der National=F6konomie, 4. revised edition, M=FCnchen. pp. 131= 
-168. 
 
Szacki, Jerzy (1981): "Schulen" in der Soziologie, in: Lepenies, Wolf  
(ed.): Geschichte der Soziologie, Studien zur kognitiven, sozialen und  
historischen Identit=E4t einer Disziplin, Vol. 2, Frankfurt/ Main, pp. 16= 
-30. 
 
Jan Pieter Schulz