Content Optimisation for UK Schools
Optimising Images & Multimedia for UK School Websites: Performance, Accessibility & Search
Published by SEO for Schools • Author: Paul Delaney
Images and multimedia do most of the storytelling on school websites—celebrating achievements, showcasing facilities, and guiding parents through key tasks. Done well, they make pages faster on mobile, more accessible to everyone, and easier for search engines to understand. This expert guide explains the complete system for UK schools: choosing modern formats, writing responsive markup, protecting Core Web Vitals, delivering captions and transcripts, applying structured data and sitemaps correctly, and governing quality across a multi-academy trust.
How search engines understand images & media
Search engines rely on surrounding context to interpret visuals: filenames, alt text, captions, headings near the media, page titles and structured data. For images and video to be indexed and surfaced correctly, they must be crawlable, fast and semantically described. Google’s documentation recommends descriptive filenames, proper alt text, responsive images and relevant structured data for media-rich pages.
References: Google Search Central — Image best practices • Video structured data • Page experience.
Formats that balance quality and speed (AVIF/WebP/MP4)
Images
- AVIF — excellent compression at high quality; use for photography when supported.
- WebP — widely supported; strong savings vs JPEG/PNG.
- PNG — lossless; best for logos or UI with crisp edges.
- SVG — vector; ideal for logos and icons, pixel-perfect at any size.
Rule of thumb: AVIF/WebP for photos, SVG for graphics, PNG/JPEG only when necessary. Keep hero images as lean as practical.
Video & audio
- Video: MP4 (H.264/AAC) for compatibility; modern codecs are fine if your stack supports them.
- Audio: AAC/MP3 for broad support; provide transcripts for key audio.
Always provide a poster image for videos and avoid auto-playing with sound.
Reference: web.dev — Fast load times.
Responsive images that truly respond
Responsive images prevent mobiles from downloading desktop-sized files. Done correctly, they are a major win for speed and data usage.
Pattern: responsive image with modern formats
<picture> <source type="image/avif" srcset="/images/library-640.avif 640w, /images/library-1024.avif 1024w, /images/library-1600.avif 1600w" sizes="(max-width: 768px) 92vw, 1080px"> <source type="image/webp" srcset="/images/library-640.webp 640w, /images/library-1024.webp 1024w, /images/library-1600.webp 1600w" sizes="(max-width: 768px) 92vw, 1080px"> <img src="/images/library-1024.jpg" srcset="/images/library-640.jpg 640w, /images/library-1024.jpg 1024w, /images/library-1600.jpg 1600w" sizes="(max-width: 768px) 92vw, 1080px" width="1080" height="608" alt="Students reading in the school library" loading="lazy" decoding="async"></picture>srcsetandsizesensure smaller downloads on mobiles.width/height(or CSSaspect-ratio) prevent layout shift (CLS).loading="lazy"defers below-the-fold images.
References: MDN — Responsive images • MDN — loading attribute.
Protecting Core Web Vitals (LCP, CLS, INP)
LCP (Largest Contentful Paint)
On school pages the LCP is usually the hero image or a large heading. Reduce LCP by compressing the hero, serving AVIF/WebP, and preloading the single true LCP image.
<link rel="preload" as="image" href="/images/hero-1024.avif" imagesrcset="/images/hero-768.avif 768w, /images/hero-1024.avif 1024w, /images/hero-1600.avif 1600w" imagesizes="(max-width: 768px) 92vw, 1080px">CLS (Cumulative Layout Shift)
Stop page “jumping” by sizing images and iframes and reserving space for banners and sticky headers. Set explicit dimensions or use aspect-ratio.
INP (Interaction to Next Paint)
Heavy galleries, sliders and third-party embeds can delay interactions. Prefer native HTML where possible, lazy-load off-screen media, and defer non-critical scripts.
References: web.dev — LCP • CLS • INP.
Accessibility essentials: alt text, captions, transcripts
Alt text that helps
- Describe the purpose of the image in context: “Year 6 pupils in coding club” not “IMG_1234”.
- Decorative images may have empty alt (
alt="") so screen readers skip them. - Never stuff keywords; write for people first.
Captions & transcripts
- Provide captions for prerecorded video and transcripts for audio to meet WCAG success criteria.
- Include the speaker’s name if it clarifies context.
- Ensure text alternatives are discoverable on mobile.
References: W3C — WCAG 2.2 Quick Reference • W3C techniques H37/H67/H96 • GOV. UK — Content design.
Privacy, UK GDPR & safeguarding when using media
- Avoid exposing pupil-identifiable information in metadata or filenames; strip EXIF data before publishing photos.
- Use neutral, respectful descriptions for safeguarding/SEND content and signpost clear routes to help.
- For third-party embeds (e.g., video), prefer privacy-enhanced modes and ensure consent/cookie banners don’t block essential content for users who decline tracking.
References: ICO — UK GDPR guidance • DfE — KCSIE • GOV. UK — Content design.
Delivery: CDNs, caching, preloading & lazy-loading
- Compression: enable Brotli or Gzip on text assets; compress images during processing/export.
- CDN: serve media from UK/EU edges; use cache-busting file names (e.g.,
hero.ab12.avif). - Caching headers: long TTL for static assets (
Cache-Control: public, max-age=31536000, immutable), short TTL for HTML. - Preload critical assets: fonts and the single hero image; don’t over-preload.
- Lazy-load below-the-fold media:
loading="lazy"for images/iframes; intersection observers for custom components.
References: web.dev — Performance • MDN — iframe loading.
Video strategy: hosting, embeds and discoverability
Where to host
- YouTube (nocookie): wide device support, captions, chapters and search visibility. Use the privacy-enhanced domain and lazy-load.
- Self-host: only for short clips with clear caching and CDN support; ensure bandwidth limits are acceptable.
<div style="position:relative;padding-top:56.25%"> <iframe loading="lazy" width="560" height="315" style="position:absolute;inset:0;width:100%;height:100%" src="https://www.youtube-nocookie.com/embed/VIDEO_ID" title="School video overview" frameborder="0" allowfullscreen></iframe></div>Make video discoverable
- Provide captions and an on-page summary.
- Add VideoObject structured data with name, description, thumbnail URL, upload date and duration.
- Include the video in your sitemap if it’s an important asset.
<script type="application/ld+json">{ "@context":"https://schema.org", "@type":"VideoObject", "name":"Welcome to [School]", "description":"Our values and facilities.", "thumbnailUrl":"https://www.seoforschools.co.uk/images/welcome-thumb.jpg", "uploadDate":"2025-09-01", "duration":"PT2M15S", "contentUrl":"https://www.seoforschools.co.uk/videos/welcome.mp4", "embedUrl":"https://www.youtube-nocookie.com/embed/VIDEO_ID"}</script>References: Google Search Central — Video structured data • Sitemaps • WCAG captions guidance.
Metadata: file names, structured data & sitemaps
- Filenames: human-readable and descriptive (
year-6-coding-club-2025.avif)—avoid camera defaults (IMG_1234. JPG). - Image licensing metadata: if you license images, include licensing metadata so rights are clear and eligible for licensable features.
- Structured data: for key media, include
ImageObject/VideoObjectvalues such ascaption,thumbnail,uploadDate. - Sitemaps: ensure important media is discoverable via XML sitemaps; don’t block assets in
robots.txtif you want them indexed.
References: Google Search Central — Image licence metadata • Image best practices.
Governance for schools and MATs
| Area | Policy | Owner | Cadence |
|---|---|---|---|
| Formats | AVIF/WebP preferred; SVG for logos; poster images mandatory for video | IT/SEO | Termly review |
| Accessibility | Alt text for meaningful images; captions for prerecorded video; transcripts for audio | SEND/Comms | Pre-publish check |
| Performance | Responsive images; LCP hero preload; lazy-load below the fold; size attributes to prevent CLS | SEO/Dev | Monthly spot-checks |
| Privacy | Strip EXIF; avoid PII; use privacy-enhanced embeds | DSL/Comms | Pre-publish check |
| Metadata | Descriptive filenames; structured data on key media; sitemap entries for priority assets | SEO | Quarterly audit |
Print-screen checklists
Images & Multimedia — 20-Point Checklist
Screenshot or print this card- Use AVIF/WebP for photos; SVG for logos/icons.
- Provide responsive
srcset/sizes. - Preload the single hero (LCP) image.
- Add
width/heightoraspect-ratio. - Lazy-load below-the-fold images/iframes.
- Use privacy-enhanced video embeds; add captions.
- Provide transcripts for audio.
- Write meaningful alt text; leave decorative images empty alt.
- Compress before upload; keep hero payloads lean.
- Strip EXIF; avoid PII in filenames.
- Use descriptive filenames.
- Add
ImageObject/VideoObjectwhere relevant. - Include key media in sitemaps.
- Set long cache for assets; hashed filenames.
- Avoid auto-playing audio; poster images for video.
- Reserve space for consent banners/sticky headers.
- Minimise heavy sliders/galleries; prefer native elements.
- Check mobile rendering on a real device.
- Confirm Core Web Vitals after changes.
- Record updates and results in a simple log.
Trust-Wide Governance
Screenshot or print this card- Approved format rules (AVIF/WebP/SVG).
- Alt/captions/transcripts standards.
- Performance guardrails (LCP/CLS/INP).
- Privacy rules (EXIF, PII, embeds).
- Quarterly media audit & roll-over tasks.
FAQs
Should we convert all existing images to AVIF/WebP?
Prioritise high-traffic templates (Home, Admissions, Term Dates, Policies) and recent posts first. Use AVIF/WebP with JPEG/PNG fallbacks; don’t re-encode graphics that are best as SVG.
Are galleries and carousels bad for performance?
They can be. Each slide is an image or video that consumes bandwidth and can delay interactions. If a carousel adds value, defer off-screen slides and provide responsive images.
Do captions and transcripts help SEO?
They make content accessible and supply indexable text that explains the media. This helps discoverability and aligns with WCAG.
Is YouTube acceptable for school privacy?
Use the privacy-enhanced domain (youtube-nocookie.com), provide captions and avoid auto-play with sound. Check your cookie/consent approach with your data protection lead.
How do we prove impact?
Track Core Web Vitals for mobile in Search Console, plus page weight and load timings in PageSpeed Insights. Watch for increases in organic CTR on media-heavy pages.
Need practical SEO support?
Speak With Paul Delaney
Paul Delaney helps schools turn complex SEO into simple, effective actions. As a guest writer for SEO for Schools, Paul shares step-by-step playbooks and evidence-based guidance that busy teams can apply immediately. With three decades’ experience working with UK and international institutions, he understands the challenges school teams face and is well positioned to offer support and guidance.
For our readers, Paul offers free 30-minute sessions for institutions exploring how to raise visibility, strengthen brand trust and streamline admissions. Sessions are practical, jargon-free and free from sales pressure. You can contact him using the buttons below—please mention SEOforSchools.co.uk.
