I think, there is no direct solution,
Let us wait until get any suggestions from Tableau Scientists.
first attach workbook sample here.
Without data set then we cannot do anything.
Please find the below steps and let me know if it worked or not. It took so much of time in forming the screenshot . So If it fulfils your requirement ,kindly mark the answer as correct answer.
1) Create a two sheet by using the same data.
make the transparency to Zero.
3) Then change the colour of the header as per your requirement in sheet 1. I have chosen Maroon. Also you modify the tooltip information by removing the undesired information from the sheet 2.
4) Then select the row/cell value which you want to make it as a bold heading . Right click on the cell and then select "keep Only". After that Hide the heading labels.it will show only "Teachers" in the sheet.
5) Then right click on Cell value and select format option .Change the colour accordingly .Also. do some modification like change the "Row Divider Pane " to None
6) Go to Dashboard the Drag both the sheet(Sheet 1 and Sheet 2) into the Horizontal pane.
Make the sheet2 "Floating " and select option "Deselect" .After that right click on Sheet 2 and select "hide title".
Overlap the sheet to one and adjust it shape.
Thanks a lot Rajeev for your support. Your solution provided above works perfectly for me.