The penultimate season of The Wire once more expands the show's focus - this time to include education primarily through the faltering Baltimore public school system. This series again has a fantastic opening with a thickly accented young soldier in the drug war named "Snoop" buying a nail gun from a hardware store and receiving thorough tutoring in its usage from the salesman - the first of many unlikely sources of education we will see in the series.

The change of focus is not entirely unexpected - the series changes up with each new season - but it is masterfully handled. After the third season there is an apparent gap in the shows cast; long-time stars Idris Elba and Wood Harris have left the show and the Barksdale drug-dealing organization is in tatters. Compounding the vacuum left by two of the shows longest serving and most fascinating character's Dominic West's Jimmy McNulty is also sidelined and does not appear in several episodes this season. It is a mark of the series' ambition that the nominal main character of the show is allowed to fade into a supporting role to accommodate new story-lines.

Stepping in to fill these gaps are four young actors each of whom creates a stunning and affecting performance. Many other shows would have layered sentiment and condescension on these middle school aged characters but The Wire grants them the same humanising approach as it does any of its characters. Tristan Wilds plays Michael Lee a quiet leader amongst his peers and strangely withdrawn with adults. Michael's journey this season was not unexpected but remains heart wrenching and the reasons for his actions are subtly revealed and upsetting. Julito McCullum plays Namond Brice, a brash and comparatively rich kid and the son of incarcerated Barksdale enforcer Wee-Bey. Namond's path was entirely unexpected for me and provides one of the series brightest moments which shine stronger for their rarity. Maestro Harrell plays Randy Wagstaff a bright and business minded foster child who counts himself lucky to have found a supportive home. Jermaine Crawford plays Duquan Weems; the most unfortunate of the four his parents are drug addicts and he is neglected. Both Randy and Dukie have difficult stories to follow. Its another ambitious step to put so much of the dramatic weight of the series in such young and unproven actors but it pays off - all four deliver textured performances that blend with the world of The Wire seamlessly.

The Stanfield Organization also have an expanded role and Jamie Hector turns in a chilling performance as ruthless and malicious drug kingpin Marlo Stanfield. Snoop, and her mentor Chris Partlow, share more screen time in this season and are both chilling and provide some of the series funnier moments. The characters of Ellis Carver, Bunny Colvin and Prez all see unexpected developments and its a joy to see actors Jim True-Frost (Prez) and Seth Gilliam (Carver) shine in their larger roles. JD Williams also shines this year as newly independent drug dealer Bodie Broadus he has some fantastic scenes with McNulty and Tray Chaney's Poot that recall the series earlier moments.

The writing continues to be top notch. David Simon gives a greater share of the responsibility to his colleague Ed Burns this time. Burns was a detective but left the department and taught in public schools for several years and his experience illuminates the series main theme. Along with Burns 'earlier career Simon's own experience as a crime reporter informs the series longest running focus - the institutional struggles and similarities of the police department and the city drug dealers. William F. Zorzi worked with Simon as a reporter but covered politics and oversees the ongoing examination of Baltimore's lawmakers. Acclaimed crime novelists George Pelecanos, Dennis Lehane and Richard Price continue to contribute episodes. It is the writers wealth of experience that brings continuing verisimilitude and depth of realism to the depiction of the city.

This is the least case driven series of the show and the scaled back investigation gives more room to accomodate the increasing scope. Its the best example of the show being an examination of the city rather than a crime/cop drama. The series makes a convincing argument about the bankruptcy of an education system that claims that no child is left behind but encourages policies such as working solely towards test scores and social promotion; as always its socially relevant and compelling stuff. This series stands well on its own because of the wealth of new characters but I'd urge anyone to start at the beginning and let the show build as intended. Its challenging viewing and rewards viewer commitment with subtleties of storytelling and rapidly increasing intensity towards the end of the series. These kids all get an education, none of the lessons are easy and few of them come from the school system.