context: Private schools in Australia may be favoured for many reasons: prestige and the social status of the 'old school tie'; better quality physical infrastructure and more facilities (e.g. playing fields, swimming pools, etc.), higher-paid teachers; and/or the belief that private schools offer a higher quality of education. Some schools offer the removal of the purported distractions of co-education; the presence of boarding facilities; or stricter discipline based on their power of expulsion, a tool not readily available to government schools. Student uniforms for Australian private schools are generally stricter and more formal than in government schools - for example, a compulsory blazer. Private schools in Australia are always more expensive than their public counterparts.[citation needed]
question: What item of clothing is considered formal and prestigious?