Here are some specific schools/organizations that may offer summer writing programs for high school students (check individual sites for the most current information, scroll down for programs specifically focused on journalism):
Adelphi University (NY) - Young Writers' Retreat: https://www.adelphi.edu/high-school-students/young-writers-retreat/
Alfred University (NY) - https://www.alfred.edu/about/community/summer-camps/virtual-camps/creative-writing-virtual-camp.cfm
American University (DC) - http://www1.american.edu/american/registrar/summer/
Appel Farm (NJ) - Appel Farm Art/Music: https://www.appelfarm.org/ (Ages 8½-17)
Bard Workshops for Writing and Thinking https://iwt.bard.edu/students (in-person and online options)
Barnard (NY) - http://www.barnard.edu/pcp
Brown (RI) - http://www.brown.edu/scs/pre-college/
Boston University (MA) - http://www.bu.edu/summer/high-school-programs/
California College of the Arts' (Oakland, CA) - http://www.cca.edu/academics/summer/precollege/index.php
California State Summer School for the Arts (Innerspark): Creative Writing - http://www.csssa.org/index.php/admissions/creative-writing/
Carleton College (MN) - http://apps.carleton.edu/campus/SAP/writing/
Choate Rosemary Hall - http://www.choate.edu/summerprograms/
Columbia College Chicago High School Summer Institute (IL) – https://learn.colum.edu
Columbia University (NY) - http://ce.columbia.edu/Summer-Program-High-School-Students-NYC
Cooper Union (NY) - http://cooper.edu/academics/outreach-and-pre-college/summer-writing
Cornell (NY) - http://www.sce.cornell.edu/sc/programs/index.php?v=159&s=Overview
Denison University (OH) – http://reynolds.denison.edu/ (The Jonathan R. Reynolds Young Writers Workshop)
Duke (NC) - http://www.learnmore.duke.edu/youth/youngwriter/ and http://www.learnmore.duke.edu/youth/creativewriter/
Emerson (MA) - https://www.emerson.edu/pre-college-programs
George Mason U Northern Va. Writing Project - http://www.nvwp.org/
Georgetown (DC) - https://frontroweducation.org (specifically focused on college application-related writing)
Hollins University - http://www.hollins.edu/summerprograms/
Idylwild Arts (CA) - http://www.idyllwildarts.org
Interlochen (MI) - http://camp.interlochen.org/creative-writing-summer-programs
Johns Hopkins - http://www.jhu.edu/summer/
Kenyon (OH) - http://www.kenyonreview.org/workshops/young-writers/
Kent School (CT) - http://www.writerscamp.org
Lake Forest College (IL) - http://www.lakeforest.edu/academics/summer/wtw/
Landmark College (VT) - http://www.landmark.edu/programs/summer/high_school_summer.cfm
Lewis & Clark - http://college.lclark.edu/programs/fir_acres/
UMass Amherst - Juniper Institute for Young Writers https://www.umass.edu/juniperyoungwriters/ "An immersive week of creative writing workshops, studio sessions, field trips, craft sessions, and readings"
Miami University of Ohio - http://www.units.muohio.edu/jrscholars/
New England Young Writers' Conference at Middlebury College (VT) - http://blogs.middlebury.edu/neywc/
(In May; application deadline is in November!)
Naropa - http://www.naropa.edu/swp/
Northeastern University (MA) - http://www.writeboston.org/summer-journalism-institute.html
Northwestern High School Institute - http://www.northwestern.edu/nhsi, plus online bootcamps: https://nhsi.northwestern.edu/online-writing-boot-camps
Pratt Institute Precollege Creative Writing Program (NY) - https://www.pratt.edu/continuing-and-professional-studies/precollege/summer-precollege
Putney School (VT) - http://www.putneyschool.org/summer
Rena's Promise (NY) - http://renaspromisecamp.wordpress.com/about/ (located at http://www.quinipet.org/)
Rhodes College (TN) - https://www.rhodes.edu/academics/summer-programs/summer-writing-institute
Sarah Lawrence (NY) - http://www.slc.edu/ce/pre-college/summer/index.html
Sewanee Writers Conference (TN) - http://www.sewanee.edu/ywc/
Shared Worlds (SC) - https://www.sharedworldscamp.com
Sheila Morrison School (Ontario, Canada) - http://www.sheilamorrisonschool.com/hacadem.html
Simon's Rock/Bard - www.simons-rock.edu/young-writers
Skidmore - http://cmsauthor.skidmore.edu/odsp/precollege/index.cfm
Stanford University EPGY Summer Institutes - http://epgy.stanford.edu/summer/hspcourseofferings.html?department=writing
Susquehanna University - https://www.susqu.edu/academics/summer-pre-college-programs/writers-workshop/
Syracuse University (NY) - http://www.summercollege.syr.edu/fictionpoetry.html
Towson University - https://wp.towson.edu/mwp/students/summer-writers-camps/
Tufts - http://ase.tufts.edu/tuftssummerstudy/writing.asp
U Iowa - http://www.uiowa.edu/~iyws/tableofcontents.htm
University of Iowa - Between the Lines - http://iwp.uiowa.edu/programs/between-the-lines
BTL is a summer program in Iowa City, Iowa, that brings together young writers from many countries for two weeks of creative writing and cultural exchange. BTL students take part in creative writing workshops, a world literatures seminar, cultural exploration activities and more. Some years they run two sessions, each one focused on a different cultural context.
UPenn - http://www.sas.upenn.edu/lps/highschool/summer
University of Rochester (NY) - http://enrollment.rochester.edu/admissions/precollege/
University of Virginia Young Writers' Workshop (VA) - http://fusion.web.virginia.edu/yww/index.cfm
UC Berkeley – Emerging Writer’s Institute - http://www.educationunlimited.com/camp/24/emerging-writers-institute.html
UC Santa Barbara - http://www.summer.ucsb.edu/
UCLA - http://www.summerfun.com/06h/index.php?pag=trip&co=summer&tid=1
University of Massachusetts Juniper Summer Writing Institute - http://www.umass.edu/juniperyoungwriters/
University of North Carolina - http://summer.unc.edu/
University of Saint Andrews (Scotland) - http://www.st-andrews.ac.uk/admissions/int/summerschools/
U of Virginia Writers Workshop - https://education.virginia.edu/services-outreach/young-writers-workshop
Walnut Hill Summer Creative Writing Program (MA & the UK) -http://why.walnuthillarts.org/writing-publishing/summer/summer-writing/
Wellesley (MA) - https://www.wellesley.edu/extended/summer
Wofford College's "Shared Worlds" camp - http://www.wofford.edu/sharedworlds/
Wolfeboro Camp School (NH) - http://www.wolfeboro.org/
Yale - http://summer.yale.edu/
Further search:
Peterson’s publishes Summer Opportunities for Kids and Teenagers in print and on the web. You can access a list of schools/ institutions/ camps that report that they offer writing in their summer programs here:
http://www.petersons.com/summerop/select/a7350se.asp
Porter Sargent also publishes guides to summer study: http://www.portersargent.com/
And there are a bunch of links here: http://www.teenink.com/Summer/
Calder Classics (various locations) - http://www.calderclassics.com
Centauri Arts Camp (Ontario, CANADA) http://www.centauri.on.ca (Ages 9-18)
Oxford/Cambridge - http://www.britishcouncil.org/usa-education-prospective-students-high-school-summer-programs-2.htm
Cambridge Pre-U Programme - http://www.cie.org.uk/qualifications/academic/uppersec/preu
Paris American Academy - http://pariswritingworkshop.com/about.html
Spoleto Study Abroad (Spoleto, ITALY) http://www.spoletostudyabroad.com Ages 15-19
Studio Art Centers (Florence, ITALY) http://www.saci-florence.org Ages 18-+
U of St Andrews-Writ (St Andrews, SCOTLAND)
http://www.st-andrews.ac.uk/admissions/int/summerschools/creativewritingsummerprogramme/
(See also the list here: http://djnewspaperfund.dowjones.com/fund/hss_directory_listing.asp)
Al Neuharth Free Spirit & Journalism Conference: https://www.freedomforum.org/al-neuharth-free-spirit-and-journalism-conference/ (selective, free if accepted)
Asian American Journalists Association J Camp (CA) - https://www.aaja.org/programs-and-initiatives/jcamp/ (special focus on multicultural perspectives)
Boston University's Academy of Media Production - http://www.academyofmediaproduction.com/
Boston University's New England Center for Investigative Reporting - http://studentprograms.necir.org/
California Scholastic Press Association Cal Poly Journalism Workshop (CA) - http://www.cspaworkshop.org/
Columbia Scholastic Press Association Summer Journalism Workshop (NY) - http://www.columbiauniversity.org/cu/cspa/docs/conventions-and-workshops/summer-workshop/index.html
Five Points (NY) - http://www.union.edu/fivepoints/academictracks/massmedia.html
Indiana University High School Journalism Institute (IN) - http://journalism.indiana.edu/programs/hsji/
Iowa Journalism and Yearbook Workshops (IA) - http://www.uiowa.edu/~journshp/
Kansas - http://ehub.journalism.ku.edu/kji/
University of Maryland's Summer Journalism Program - http://www.journalism.umd.edu/mspa/summer/index.html
Michigan Interscholastic Press Association Summer Journalism Workshop (MI) - http://mipamsu.org/
North Carolina Scholastic Media Institute (NC) - http://www.ibiblio.org/ncsma/institute.html
Northwestern University Medill "Cherubs" (IL) - http://www.medillcherubs.org/
Carolina Journalism Institute (SC) - http://www.sc.edu/cmcis/so/cji/index.html
U of Florida Summer Journalism Institute (FL) - http://www.jou.ufl.edu/sji/
U of Mississippi Journalism Institute (MS) - http://www.outreach.olemiss.edu/Summer_High_School/high_school/programs/journalism.html
Virginia Tech High School Journalism Camp (VA) - http://www.collegemedia.com/jcamp/
WYHH Young Journalists Camp (Philadelphia) - two sessions, http://www.whyy.org/hamiltoncommons/programs.html
HS students with an interest in submitting their work in historical research for publication may want to check out The Concord Review:
" Since 1987, The Concord Review, a unique quarterly academic journal at the secondary level, has published 80 issues with 879 high school history research papers by students from 44 states and 35 other countries. Essays of around 6,000 words or more (the average length of papers in the Spring 2009 issue was 7,927 words), with (Chicago style) endnotes and bibliography, on any historical topic (ancient or modern, domestic or foreign), may be submitted, with a completed copy of the Form to Accompany Essays (from www.tcr.org), and a check for $40 made out to The Concord Review, to: The Concord Review, 730 Boston Post Road, Suite 24, Sudbury, Massachusetts 01776 USA. The author receives the next four issues of the journal. We publish about 7% of the essays we receive. "