* A school that operates during the late afternoon/early evening: This is the most likely meaning. It's essentially a school that offers classes after the typical school day ends, often to accommodate students with work or other commitments. This might be for regular academic subjects or for extracurricular enrichment.
* A school with a focus on specific subjects offered in the evening: For example, a school might offer "twilight photography classes" or "twilight creative writing workshops," meaning these classes are held during the evening.
* Informal or metaphorical use: The term could be used figuratively to describe a less formal or less structured educational setting, perhaps one that happens informally in the late afternoon or evening.
Without more information about where you encountered the term "twilight school," it's impossible to say for certain what it means in that specific instance. If you provide more context, I can give you a more precise answer.