CRPD/C/GC/4 inclusive education environments, qualified in sign language and/or Braille and with orientation and mobility skills. Having an adequate number of qualified and committed school staff is key to the introduction and sustainability of inclusive education. Lack of understanding and capacity remain significant barriers to inclusion. States parties must ensure that all teachers are trained in inclusive education and that that training is based on the human rights model of disability. 37. States parties must invest in and support the recruitment and continuous education of teachers with disabilities. This includes removing any legislative or policy barriers requiring candidates to fulfil specific medical eligibility criteria and the provision of reasonable accommodations for their participation as teachers. Their presence will serve to promote equal rights for persons with disabilities to enter the teaching profession, bring unique expertise and skills into learning environments, contribute to breaking down barriers and serve as important role models. 38. To give effect to article 24 (5), States parties should ensure that persons with disabilities are able to access general tertiary education, vocational training, adult education and lifelong learning without discrimination and on an equal basis with others. Attitudinal, physical, linguistic, communication, financial, legal and other barriers to education at these levels must be identified and removed in order to ensure equal access. Reasonable accommodation must be provided to ensure that persons with disabilities do not face discrimination. States parties should consider taking affirmative action measures in tertiary education in favour of learners with disabilities. III. Obligations of States parties 39. States parties should respect, protect and fulfil each of the essential features of the right to inclusive education: availability, accessibility, acceptability and adaptability. The obligation to respect requires avoiding measures that hinder the enjoyment of the right, such as legislation excluding certain children with disabilities from education, or the denial of accessibility or reasonable accommodation. The obligation to protect requires taking measures that prevent third parties from interfering with the enjoyment of the right, for example, parents refusing to send girls with disabilities to school, or private institutions refusing to enroll persons with disabilities on the basis of their impairment. The obligation to fulfil requires taking measures that enable and assist persons with disabilities to enjoy the right to education, for example, ensuring that educational institutions are accessible and that education systems are adapted appropriately with resources and services. 40. Article 4 (2) requires that States parties take measures to the maximum of their available resources regarding economic, social and cultural rights and, where needed, within a framework of international cooperation, with a view to achieving progressively the full realization of those rights. Progressive realization means that States parties have a specific and continuing obligation to move as expeditiously and effectively as possible towards the full realization of article 24. 12 This is not compatible with sustaining two systems of education: a mainstream education system and a special/segregated education system. Progressive realization must be read in conjunction with the overall objective of the Convention to establish clear obligations for States parties in respect of the full realization of the rights in question. Similarly, States parties are encouraged to redefine budgetary allocations for education, including by transferring part of their budgets to the development of inclusive education. Any deliberately retrogressive measures in that regard must not 12 See Committee on Economic, Social and Cultural Rights, general comment No. 3 (1990) on the nature of States parties’ obligations, para. 9. 11