night school

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A school that holds classes in the evening.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A school, typically used for the purpose of continuing education with classes held predominately in the evening to accommodate students with typical day shift work schedules.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a school that holds classes in the evenings for students who cannot attend during the day