It is the intent and purpose of the Legislature that the money appropriated for the purposes of this article be expended primarily for the employment of teachers to the end that the number of pupils in the designated grades in relation to each full-time equivalent classroom teacher be reduced to and sustained at a ratio of 25 to 1. Emphases shall be placed on kindergarten and primary grades for the purpose of continuing to provide small classes for children with preschool experiences. The Director of Compensatory Education shall consider this intent in approving projects submitted pursuant to this article. In the event an applicant district is unable to employ the number of teachers necessary to effect the purposes of this article, the Director of Compensatory Education, notwithstanding the provisions of Section 54480, is authorized to approve projects that provide for the employment of noncertificated teachers’ aides for grades kindergarten or 1 through 6, inclusive, to the end that the number of pupils in those grades in relation to the number of both classroom teachers and teachers’ aides employed for such grades shall not exceed 20 to 1. All teachers’ aides shall be trained in a specially designed in-service education program. Not more than 25 percent of the total allocated to a school district shall be devoted to the employment of teachers’ aides. The use of any portion of the total allocated shall be approved for the employment of noncertificated teachers’ aides by the Director of Compensatory Education only upon certification of the applicant district, approved by the county superintendent of schools which has jurisdiction over the applicant district, that teachers are unavailable for employment in accordance with the primary legislative intent of this article.