|
K12
INC
|
|
(Name
of Issuer)
|
|
Common
|
|
(Title
of Class of Securities)
|
|
48273U10
|
|
(CUSIP
Number)
|
|
December 31,
2009
|
|
*
|
The remainder of
this cover page shall be
filled out for a reporting
person's initial filing on this form with respect to
the subject class of securities, and for any subsequent
amendment containing information which would alter the
disclosures provided in a prior cover
page.
|
|
1.
|
NAME
OF REPORTING PERSONS
|
|
I.R.S.
IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
|
|
|
William
Blair & Company, L.L.C.
|
|
|
36-2214610
|
|
|
2.
|
CHECK
THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
|
|
(a) £
|
|
|
(b) £
|
|
|
3.
|
SEC
USE ONLY
|
|
4.
|
CITIZENSHIP
OR PLACE OF ORGANIZATION
|
|
222
W Adams
|
|
|
Chicago, IL
60606
|
|
|
NUMBER
OF
|
5.
|
SOLE
VOTING POWER
|
|
SHARES
|
2194483
|
|
|
BENEFICIALLY
|
6.
|
SHARED
VOTING POWER
|
|
OWNED
BY
|
-0-
|
|
|
EACH
|
7.
|
SOLE
DISPOSITIVE POWER
|
|
REPORTING
|
2194483
|
|
|
PERSON
|
8.
|
SHARED
DISPOSITIVE POWER
|
|
WITH
|
-0-
|
|
9.
|
AGGREGATE
AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
|
|
2194483
|
|
|
10.
|
CHECK
BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN
SHARES*
|
|
£
|
|
|
11.
|
PERCENT
OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
|
|
7.43%
|
|
|
12.
|
TYPE
OF REPORTING PERSON*
|
|
BD,
IA
|
|
|
Item
1(a).
|
Name
of Issuer:
|
|
Item
1(b).
|
Address
of Issuer's Principal Executive
Offices:
|
|
Item
2(a).
|
Name
of Person Filing:
|
|
Item
2(b).
|
Address
of Principal Business Office, or if None,
Residence:
|
|
Item
2(c).
|
Citizenship:
|
|
Item
2(d).
|
Title
of Class of Securities:
|
|
Item
2(e).
|
CUSIP
Number:
|
|
Item
3.
|
If
This Statement is Filed Pursuant to Rule
13d-1(b), or 13d-2(b) or (c), Check Whether the Person Filing is
a:
|
|
|
(a)
T
|
Broker
or dealer registered under Section 15 of the Exchange
Act.
|
|
|
(b)
£
|
Bank
as defined in Section 3(a)(6) of the Exchange
Act.
|
|
|
(c)
£
|
Insurance
company as defined in Section 3(a)(19) of the Exchange
Act.
|
|
|
(d)
£
|
Investment
company registered under Section 8 of the Investment Company
Act.
|
|
|
(e)
T
|
An
investment adviser in accordance with Rule
13d-1(b)(1)(ii)(E);
|
|
|
(f)
£
|
An
employee benefit plan or endowment fund in accordance with Rule
13d-1(b)(1)(ii)(F);
|
|
|
(g)
£
|
A
parent holding company or control person in accordance with Rule
13d-1(b)(1)(ii)(G);
|
|
|
(h)
£
|
A
savings association as defined in Section 3(b) of the Federal Deposit
Insurance Act;
|
|
|
(i)
£
|
A
church plan that is excluded from the definition of an investment company
under Section 3(c)(14) of the Investment Company
Act;
|
|
|
(j)
£
|
Group,
in accordance with Rule
13d-1(b)(1)(ii)(J).
|
|
Item
4.
|
Ownership.
|
|
|
(a)
|
Amount
beneficially owned:
|
|
|
(b)
|
Percent
of class:
|
|
|
(c)
|
Number
of shares as to which such person
has:
|
|
|
(i)
|
Sole
power to vote or to direct the vote
|
|
|
(ii)
|
Shared
power to vote or to direct the vote
|
|
|
(iii)
|
Sole
power to dispose or to direct the disposition
of
|
|
|
(iv)
|
Shared
power to dispose or to direct the disposition
of
|
|
Item
5.
|
Ownership
of Five Percent or Less of a Class.
|
|
Item
6.
|
Ownership
of More Than Five Percent on Behalf of Another
Person.
|
|
Item
7.
|
Identification
and Classification of the Subsidiary Which Acquired the
Security Being Reported on by the
Parent Holding Company or Control
Person.
|
|
Item
8.
|
Identification and Classification of
Members of the Group.
|
|
Item
9.
|
Notice
of Dissolution of Group.
|
|
Item
10.
|
Certifications.
|
|
January 15, 2010
|
||
|
(Date)
|
||
|
/s/ Michelle Seitz
|
||
|
(Signature)
|
||
|
Principal & Manager of Investment
Services
|
||
|
(Name/Title)
|