Article: Pāśupata Shaivism (Pāśupata, "of Paśupati") is the oldest of the major Shaiva schools. The philosophy of Pashupata sect was systematized by Lakulish in the 2nd century CE. Paśu in Paśupati refers to the effect (or created world), the word designates that which is dependent on something ulterior. Whereas, Pati means the cause (or principium), the word designates the Lord, who is the cause of the universe, the pati, or the ruler. Pashupatas disapproved of Vaishnava theology, known for its doctrine servitude of souls to the Supreme Being, on the grounds that dependence upon anything could not be the means of cessation of pain and other desired ends. They recognised that those depending upon another and longing for independence will not be emancipated because they still depend upon something other than themselves. According to Pāśupatas, soul possesses the attributes of the Supreme Deity when it becomes liberated from the 'germ of every pain'.

Now answer this question: What is the oldest school of Shaivism?
Pāśupata Shaivism