Yes, a student from a semi-English medium school can generally apply for admission to a Sainik School , but there are a few important points to consider:

1. Medium of Instruction : Sainik Schools typically use English as the medium of instruction. Therefore, students should have a reasonable proficiency in English to cope with the curriculum effectively. If the student's English skills are not strong, it might be beneficial to improve them before applying.

2. Admission Test : Sainik Schools conduct an entrance exam, which usually includes subjects like Mathematics, General Knowledge, and English. Proficiency in English will help in this examination, so preparation in this area is crucial.

3. Eligibility Criteria : Make sure to check the specific eligibility criteria for the Sainik School you're interested in. These criteria can include age limits, educational qualifications, and other requirements.

4. Preparation : If you are from a semi-English medium school and are concerned about the English proficiency required, consider additional English language courses or tutoring to strengthen your skills.

5. School Policy : Each Sainik School might have its own policy regarding the language medium of previous schooling, so it's a good idea to reach out to the specific school for detailed information.

Preparing well for the entrance exam and working on English language skills will enhance the chances of successful admission.

Hope it helps !