Harassing by HM through biased period allotment

Welcome to the forum!
Leveling a charge against a superior may be counterproductive if you cannot substantiate it with proper evidence/documentation. HM’s job is to allot classes to an AT. That cannot solely be a ground for grievance against him. But as you alleged, if he uses this power to harass somebody,you have to prepare the case for you with hard evidence before moving any further. You may collect the data of class allotment over a period of time and if it is out of proportion and beyond the max. number prescribed per week then you may file a written complaint to Academic Council, M.C, and then even to DI one after another. But be sure first about the intention of the HM.
Hope this helps.

as per rule you are designated to take 25 class room teaching classes.(i) if the hm whimsically yields more load you must gather the documents and apply to the mc, di simultaneously.(ii)if your load is more than others ,it should be treated in the same way.