The primary website where middle school entrance examination scores are typically accessed in the United States is the individual school district's website. Each school district has its own system for posting and disseminating scores to students and their parents. For instance, the Los Angeles Unified School District (LAUSD) uses its official website to provide access to middle school entrance exam scores. This is because the process of score release is district-specific, and each district may have different protocols for handling and publishing these scores.

The reason for this varied approach is rooted in the decentralized nature of the American education system. Unlike some other countries where national exams are standardized and scores are centrally managed, the United States allows for a high degree of autonomy at the local level. This autonomy extends to the handling of entrance exam scores, which are often used to determine which middle school a student will attend.

According to a report by the National Center for Education Statistics (NCES), approximately 80% of school districts in the United States use standardized entrance exams for middle school placement. The NCES also notes that the majority of these districts have their own systems for reporting scores, which can lead to inconsistencies in how and when scores are made available to students and parents.

For example, the New York City Department of Education uses its SchoolMatter platform to release middle school entrance exam scores. In contrast, the Chicago Public Schools (CPS) utilize their own online portal for score distribution. These differences highlight the diverse range of practices across the country.

In conclusion, the website where middle school entrance examination scores can be found is typically the official website of the student's school district. This decentralized approach is a reflection of the broader autonomy granted to local educational authorities in the United States.