| Inns | HS |
| 309-9 | 76 | Harrow Wanderers v Old Whitgiftians | Whitgift School, Croydon | 2003 |
| 279-8 | 74 | Harrow Wanderers v Old Cheltonians | Harrow School Cricket Ground, Harrow-on-the-Hill | 2012 |
| 270 | 68 | Harrow Wanderers v Old Westminsters | Vincent Square, Westminster | 2008 |
| 263 | 92 | Harrow Wanderers v Old Cheltonians | College Ground, Cheltenham | 1997 |
| 258-8 | 47* | Harrow Wanderers v Sherborne Pilgrims | Harrow School Cricket Ground, Harrow-on-the-Hill | 2002 |
| 256 | 83 | Harrow Wanderers v Downside Wanderers | Downside School, Stratton-on-the-Fosse | 2024 |
| 255-8 | 81 | Harrow Wanderers v Old Cholmeleians | Harrow School Cricket Ground, Harrow-on-the-Hill | 1992 |
| 252-9 | 54 | Harrow Wanderers v Old Brightonians | Harrow School Cricket Ground, Harrow-on-the-Hill | 2015 |
| 251-8 | 91 | Harrow Wanderers v Repton Pilgrims | Harrow School Cricket Ground, Harrow-on-the-Hill | 2004 |
| 248-4 | 77 | Harrow Wanderers v Old Cliftonians | Clifton College Close Ground, Clifton | 2014 |
| 239-4 | 43 | Harrow Wanderers v Marlborough Blues | Harrow School Cricket Ground, Harrow-on-the-Hill | 1994 |
| 235-8 | 68 | Harrow Wanderers v Shrewsbury Saracens | Shrewsbury School, Shrewsbury | 1996 |
| 235 | 76 | Harrow Wanderers v Bradfield Waifs | Bradfield College, Reading | 1996 |
| 234-4 | 63* | Harrow Wanderers v Shrewsbury Saracens | Harrow School Cricket Ground, Harrow-on-the-Hill | 1997 |
| 230 | 92 | Harrow Wanderers v Haileybury Hermits | Harrow School Cricket Ground, Harrow-on-the-Hill | 1998 |
| 229-9 | 43 | Harrow Wanderers v Old Malvernians | Malvern College Ground, Malvern | 1982 |
| 226-8 | 91 | Harrow Wanderers v St Edward's Martyrs | St Edward's School Ground, Oxford | 2013 |
| 221 | 57 | Harrow Wanderers v Bradfield Waifs | Bradfield College, Reading | 2017 |
| 220 | 73 | Harrow Wanderers v Oundle Rovers | Oundle School Ground, Oundle | 1999 |
| 220 | 92 | Harrow Wanderers v Repton Pilgrims | Harrow School Cricket Ground, Harrow-on-the-Hill | 2005 |
| 218-9 | 88 | Harrow Wanderers v Oundle Rovers | Oundle School Ground, Oundle | 1985 |
| 218-1 | 98* | Harrow Wanderers v Old Merchant Taylors | Merchant Taylors' School Ground, Northwood | 2018 |
| 215-6 | 81 | Harrow Wanderers v Felsted Robins | Felsted School Ground, Dunmow | 1998 |
| 212-9 | 91 | Harrow Wanderers v Old Merchant Taylors | Harrow School Cricket Ground, Harrow-on-the-Hill | 1993 |
| 211 | 73 | Harrow Wanderers v Sherborne Pilgrims | Sherborne School, Sherborne | 1985 |
| 208-9 | 54 | Harrow Wanderers v Oundle Rovers | Harrow School Cricket Ground, Harrow-on-the-Hill | 1975 |
| 207-7 | 61* | Harrow Wanderers v Radley Rangers | Radley College Bigside Ground, Abingdon | 1968 |
| 207-7 | 96 | Harrow Wanderers v Repton Pilgrims | Repton School Ground, Repton | 2001 |
| 206-9 | 81 | Harrow Wanderers v Old Cliftonians | Harrow School Cricket Ground, Harrow-on-the-Hill | 1973 |
| 206-5 | 92 | Harrow Wanderers v Old Tonbridgians | Tonbridge School Ground, Tonbridge | 1990 |
| 204-6 | 56 | Harrow Wanderers v Old Cliftonians | Clifton College Close Ground, Clifton | 1990 |
| 202 | 55 | Harrow Wanderers v Uppingham Rovers | Harrow School Cricket Ground, Harrow-on-the-Hill | 1968 |
| 201-9 | 62 | Harrow Wanderers v Old Wykehamists | Ridding Field, Winchester | 2012 |
| 200-8 | 72 | Harrow Wanderers v Uppingham Rovers | Harrow School Cricket Ground, Harrow-on-the-Hill | 1975 |
