Calculating hours using pivot table

Your inquiry has been up for several days without a reply. I can't speak for others with certainty, but from my perspective I suspect that the reason for the lack of replies is that the sample data you do give is far too simple. Far too simple to create a Pivot Table from; so in effect you're asking anybody who might want to offer assistance to create their own more complete set of data. 

You would help us help you by posting a more representative set of data (still no real names) with multiple teachers, multiple classes, etc. If you're not able to attach an actual Excel workbook to your reply in this forum, put it onto Google Sheets or the equivalent and paste a link here.