Hi Polar,
The Strutt's school admission registers form part of the overall book keeping system for their cotton spinning business and as such are precise records.  The 3 Mason children you have, Will, Jacob and John, are incorrect because the trade of their Father was "White Smith" and you know that George Mason was a TAILOR.
The school registers have the following headings
NAME  AGE   RESIDENCE  FATHER'S TRADE  ADMISSION ON   LEFT ON OBSERVATIONS,REASON
                                                                                                              FOR LEAVING
The children you should have are:-
George Mason   9   Gutter            Taylor          21.2.1821          7.12.1821   Gone to work at mill
Will Mason        6   Gutter            Taylor            7.3.1821         12.3.1821     Wanted
Samuel Mason   7   Gutter            Nailer          21.6.1824         27.8.1824     Another School
The comment "Wanted" does not mean anything sinister, he had failed to give a reason why he
was not attending school.
Re Samuel, the trade Nailer could be an error either by the child or the teacher, the date of leaving is also incorrect. However if you follow through with Samuel you will see that on his two marriage he states his father was George Mason a Tailor.
1.  married 12.2.1839 Duffield Harriet Timperley (he was a Potter)
2.  married 10.12.1848 St. Peters, Derby Betsy Booth both were widowed and the witnesses were
     William Mason and George Hadley.
Samuel can be found in 1841 Census, Greenhill Lane, Alfreton occupation "Bottle Maker"
The Gutter today is in the Nottingham Road Area of Belper near to where the pot works were, these later moved to Denby and is present day Denby Pottery.
Spendlove