2 answers
Hi @Tannu Priya
Ideally , you should try to get this changed at source, as it won't be only you that's affected. In the meantime, it is possible to change the value of a dimension in Tableau Desktop by creating an alias.
In the data pane, right click on the dimension (School Name in this instance) and select Aliases.
https://help.tableau.com/current/pro/desktop/en-us/datafields_fieldproperties_aliases_ex1editing.htm
Regards
Donna