| Inns | HS |
| 258-8 | 47* | Harrow Wanderers v Sherborne Pilgrims | Harrow School Cricket Ground, Harrow-on-the-Hill | 2002 |
| 239-4 | 43 | Harrow Wanderers v Marlborough Blues | Harrow School Cricket Ground, Harrow-on-the-Hill | 1994 |
| 229-9 | 43 | Harrow Wanderers v Old Malvernians | Malvern College Ground, Malvern | 1982 |
| 196-6 | 45* | Harrow Wanderers v Felsted Robins | Harrow School Cricket Ground, Harrow-on-the-Hill | 2005 |
| 192-8 | 47 | Harrow Wanderers v Old Cholmeleians | Harrow School Cricket Ground, Harrow-on-the-Hill | 1982 |
| 187 | 34 | Harrow Wanderers v Charterhouse Friars | Harrow School Cricket Ground, Harrow-on-the-Hill | 2009 |
| 174-8 | 43 | Harrow Wanderers v Old Wellingtonians | Harrow School Cricket Ground, Harrow-on-the-Hill | 2001 |
| 166 | 42 | Harrow Wanderers v Rugby Meteors | Harrow School Cricket Ground, Harrow-on-the-Hill | 1973 |
| 165 | 38 | Harrow Wanderers v Old Merchant Taylors | Durrants Sports Ground, Croxley Green | 1983 |
| 164-9 | 36 | Harrow Wanderers v St Edward's Martyrs | Harrow School Cricket Ground, Harrow-on-the-Hill | 1969 |
| 163-8 | 36 | Harrow Wanderers v Downside Wanderers | Harrow School Cricket Ground, Harrow-on-the-Hill | 1982 |
| 162-4 | 49 | Harrow Wanderers v Old Cholmeleians | Harrow School Cricket Ground, Harrow-on-the-Hill | 1981 |
| 162 | 34 | Harrow Wanderers v Oundle Rovers | Harrow School Cricket Ground, Harrow-on-the-Hill | 1991 |
| 162-8 | 37 | Harrow Wanderers v Old Cranleighans | Jubilee, Cranleigh School | 2016 |
| 156-7 | 38* | Harrow Wanderers v Old Brightonians | Brighton College Ground, Brighton | 2013 |
| 147-8 | 40* | Harrow Wanderers v Marlborough Blues | Harrow School Cricket Ground, Harrow-on-the-Hill | 1975 |
| 144 | 41 | Harrow Wanderers v Rugby Meteors | Rugby School Ground, Rugby | 2012 |
| 140 | 29 | Harrow Wanderers v Haileybury Hermits | Haileybury College Ground, Hertford | 1991 |
| 138-5 | 41 | Harrow Wanderers v Old Tonbridgians | Tonbridge School Ground, Tonbridge | 1993 |
| 138-9 | 30 | Harrow Wanderers v Old Cheltonians | Harrow School Cricket Ground, Harrow-on-the-Hill | 1995 |
| 137 | 46 | Harrow Wanderers v Old Malvernians | Burton's Court, Chelsea | 1975 |
| 135 | 33* | Harrow Wanderers v Old Malvernians | Burton's Court, Chelsea | 1968 |
| 131-6 | 31 | Harrow Wanderers v Charterhouse Friars | Harrow School Cricket Ground, Harrow-on-the-Hill | 1996 |
| 129 | 21 | Harrow Wanderers v Old Cheltonians | College Ground, Cheltenham | 2014 |
| 124 | 48 | Harrow Wanderers v Old Malvernians | Vincent Square, Westminster | 1990 |
| 119 | 41 | Harrow Wanderers v Stowe Templars | Stowe School Ground, Stowe | 2025 |
| 112 | 29 | Harrow Wanderers v Old Tonbridgians | Tonbridge School Ground, Tonbridge | 1984 |
| 111 | 42 | Harrow Wanderers v Shrewsbury Saracens | Shrewsbury School, Shrewsbury | 2022 |
| 105 | 41 | Harrow Wanderers v Charterhouse Friars | Charterhouse School, Godalming | 1972 |
| 105-3 | 44 | Harrow Wanderers v Shrewsbury Saracens | Harrow School Cricket Ground, Harrow-on-the-Hill | 2001 |
