By county

High School HS code
Washington, DC 
Georgetown Day 423466
Maret 423622
St. Albans 423711
St. Anselm's Abbey 423755
St. John's College 423788
Woodrow Wilson 423955
Baltimore City 
Digital Harbor 476366
Friends School of Baltimore 476399
Gilman 476488
Baltimore Polytechnic 476655
Allegany County 
Center for Career and Technical Education 517388
Anne Arundel County 
Arundel 526188
Chesapeake Science Point 526288
Indian Creek 526333
North County 526388
Severna Park 526633
Severn School 526655
Baltimore County 
Catonsville 533311
Chesapeake 533355
Dulaney 533377
Franklin 533511
Hereford 533588
Loyola Blakefield 533633
Park School of Baltimore 533700
St. Paul's School 533933
St. Timothy's School 533939
Towson 533944
Mount de Sales Academy 533988
Calvert County 
Calverton 545211
Huntingtown 545499
Northern 545622
Carroll County 
Liberty High School 568566
Cecil County 
Tome School 572893
Charles County 
North Point 583700
Frederick County 
Frederick 626377
Middletown 626588
Urbana 626766
Tuscarora 626788
Frederick Area Homeschoolers 626999
Garrett County 
Harford County 
Aberdeen 647122
C. Milton Wright 647866
Howard County 
Atholton 652244
Centennial 652355
Chapelgate Christian Academy 652366
Glenelg 652466
Hammond 652577
Marriott's Ridge 652711
Mt. Hebron 652733
River Hill 652811
Wilde Lake 652833
Chesapeake Math Program 652999
Kent County 
Montgomery County 
Academy of the Holy Cross 722222
Bullis School 722355
Bethesda-Chevy Chase 722366
Winston Churchill 722377
Clarksburg 722381
Gaithersburg 722466
Good Counsel 722477
The Heights School 722499
Walter Johnson 722511
John F. Kennedy 722522
Magruder 722533
Richard Montgomery 722577
Montgomery Blair 722588
Northwood 722603
Poolesville 722688
St. Andrew's Episcopal 722722
Sandy Spring Friends School 722733
Sherwood 722755
Springbrook 722799
Wheaton 722800
Walt Whitman 722811
Watkins Mill 722822
Thomas S. Wootton 722844
Takoma Park Middle School 722888
Prince George's County
Bishop McNamara 766288
Bowie 766311
Chesapeake Math & IT Academy 766455
Eleanor Roosevelt 766522
Northwestern 766777
Oxon Hill 766811
Queen Anne's County 
Kent Island 818344
Saint Mary's County 
Great Mills 825511
Leonardtown 825644
St. Mary's Ryken 825833
Talbot County 
Washington County 
Boonsboro 854277
North Hagerstown 854688
St. James 854700
Wicomico County 
James M. Bennett 862255
Salisbury Christian School 862688
Worcester County 
Snow Hill 873711