[Chaosua]

that must be realized in core. There are many quest with Practice on Training dummies
Or you can script SmartAI (trinity) EventAI (mangos) and replace coreside script for that dummies
That quest have killcredit ID always 44175 (as I saw)
On Trinity I made this like

        void SpellHit(Unit* caster, const SpellInfo* spell) OVERRIDE
        {
            //IMPLEMENTED questRewards Training skills on 3rd Level
            if (caster->GetTypeId() == TYPEID_PLAYER)
                if (spell->Id == 20271 || spell->Id == 100 || spell->Id == 2098 || spell->Id == 56641 || spell->Id == 5143 || spell->Id == 73899 || spell->Id == 348 || spell->Id == 5143)
                //if (caster->ToPlayer()->GetQuestStatus(27091) != QUEST_STATUS_COMPLETE || caster->ToPlayer()->GetQuestStatus(14013) != QUEST_STATUS_COMPLETE || caster->ToPlayer()->GetQuestStatus(25147) != QUEST_STATUS_COMPLETE) etc
                    caster->ToPlayer()->KilledMonsterCredit(44175, 0);
        }

magic numbers (who cares ) who want will change it