The story of Kavasha is
here and
here (Haug's translation). During the period of entire Rig (samhitas), varna vyavastha was not in force. But after the period of Samhitas came the period of Brahmanas (texts); wherein elaborate sacrifices were created (Refer
here and
here). During this period (when Brahmanas (texts) were composed or created), there was intense struggle for the office of brahmana. At this time, the shudras were already a demarcated group (infact all thru the vedic samhita period also the asuras / dasyus were an inimical group, however they were not enslaved yet). In this particular story Kavasa was the son of a rishi from a shudra (slave) woman. He was a product of anuloma (brahman father, shudra mother).
When Kavasa sought to take part in the soma yagna (sacrifice), the other rishis (madhyamas) derided him. But Saraswati came to his rescue and declared Kavasa guiltless. Then Kavasha was accepted in the sacrifice. This merely shows shudras were unacceptable in yagnas. No less than a personage as Sarasvati herself had to declare him guiltless (due to his birth). Infact the other rishis had driven out Kavasa to die of thirst. At this time he 'saw' (composed) mantras (kindly note there is no evidence he was taught vedas, instead he composed mantras himself which became part of vedic brahmanas (texts)). Possibly since Kavasha was an achiever (composer plus killer of rakshasas), he made his place amongst brahmans. Sorry Vaagmi, this point does not show Shudras were taught vedas. Infact you said Gavasha was a panchama -- sorry but nowhere is Kavasha called a panchama.
It is
here (Sanskrit version is
here). Where is Kakshivant called a shudra ?
Please can you provide the verse where he is called a shudra?
Sorry Vaagmi, it turns out jAnasruti was not a shudra; whilst Kavasha was born of a brahman father and shudra mother (he was part brahman yet had to face such troubles and ostracism). As for Kakshivant, nowhere is he called a shudra. Finally wrt Satyakama Jabala, there is no evidence he was a chandala (his father was unknown).
Thank you.