This could help point you in correct direction, regardless of the number of accidents

CREATE TABLE #tblDrivers (DriverID Int, AccidentDate date)

INSERT INTO #tblDrivers(DriverID,AccidentDate)

VALUES (1,'03/01/2012'),

(1,'05/06/2015'),

(2,'08/05/2013'),

(3,'12/01/2011'),

(4,'06/22/2005'),

(4,'04/01/2008'),

(4,'11/21/2010')

GO

CREATE TABLE #tblDrivingSchool (DriverID Int, ClassDate date)

INSERT INTO #tblDrivingSchool (DriverID,ClassDate)

values

(1,'03/15/2012'),

(3,'12/18/2011'),

(4,'07/10/2005')

;

With

Driver_Accident_History as

( Select

a.DriverID

,a.AccidentDate

,ROW_NUMBER() over (partition by a.DriverID order by a.AccidentDate) as Accident_Number

from #tblDrivers a

group by

a.DriverID

,a.AccidentDate)

Select

a.DriverID

,a.Accident_Number

,a.AccidentDate

,count(b.ClassDate) as Driving_classes_Attended_Prior_To_Accident

,max(b.ClassDate) as Last_Driving_classes_Prior_To_Accident

,count(c.ClassDate) as Driving_classes_Attended_After_Accident

,min(c.ClassDate) as First_Driving_classes_After_Accident

from Driver_Accident_History a

left join #tblDrivingSchool b on a.DriverID = b.DriverID and b.ClassDate <= a.AccidentDate

left join #tblDrivingSchool c on a.DriverID = c.DriverID and c.ClassDate > a.AccidentDate

Group by

a.DriverID

,a.Accident_Number

,a.AccidentDate

Drop table #tblDrivers,#tblDrivingSchool