There were three HLTAs at my old school about same size as you describe. They covered PPA AHT time SENco time nothing else. This was for most p.ms. TAs for rest of their employment. My present school has no HLTAs,smaller school all PPA and absences covered by supply teachers . They have two TAs who are HLTAs but they are not employed as such. What do your HLTAs do? If covering PPA can just one now cover? Will this mean job cuts for some?