The only way to ascertain if a phonics only approach is any more effective than mixed methods would be to establish if this absorbs less teaching time. In the famous Clackmananshire study, children in the SP group received far more teaching, especially if they were showing signs of falling behind.
With English spelling being what it is, time devoted to teaching is what makes the big difference after initial phonics. It comes down to meeting the words which are tricky in some way, like 'any, many, once, other, only', often enough for them to become firmly fixed in pupils minds so they know how pronounce them without hesitation.
Nobody doubts the value of some phonics - of teaching the main sounds of the 81 main English spellings, i.e. the first one on the list below - although phonics fanatics claim that such teachers exist. After that it's a matter of sufficient recurring exposure of words with tricky bits in them, i.e. graphemes with more than one pronunciation.
The following table shows the English spelling system and its irregularities for the 44 English sounds.
(The figures in brackets show how many of the 7,000 most used English words which I have analysed use that spelling - and how many spell it differently.)
- a: cat – plait, meringue (466 – 3)
- a-e: plate – wait, weight, straight, great, table dahlia, fete (338 – 69)
-ain: rain – lane, vein, reign, champagne (39 – 19)
-ay: play – they, weigh,ballet,cafe, matinee (35 – 20)
- air: care – hair, bear, aerial, their, there, questionnaire (31-are – 27 other)
- ar: car – are + (Southern Engl. bath) (138 – 1)
- au: sauce – caught, bought,always, tall, crawl (44 au – 76 other)
-aw: saw – (0)- but in UK 11-aw + 40 awe, or, four, sore, war
- b: bed (0)
- ca/o/u: cat, cot, cut – character, kangaroo, queue (1022 – 33)
cr/cl: crab/ clot – chrome, chlorine (192 – 10)
-c: lilac –stomach, anorak (89 – 9)
-ck: neck –cheque, rec (62 – 6)
k: kite/ kept – chemistry (124 – 7)
-k: seek –unique (36 – 5)
-sk: risk –disc, mosque (86 – 10)
qu: quick – acquire, choir (78 – 4)
x: fix – accept, except, exhibit (98 – 15)
- ch: chest – cello (155 – 1)
-tch: clutch – much (24 – 7)
9 d: dad – add, blonde (1,010 – 3)
10. e: end– head, any, said, Wednesday, friend, leisure,
leopard, bury (301 – 67)
11. er: her – turn, bird, learn, word, journey (70er – 124)
12. ee: eat– eel, even, ceiling, field, police,people,
me, key,ski, debris, quay (152ea – 304)
--y: jolly– trolley, movie, corgi (475 – 39)
13. f: fish– photo, stuff, rough (580 - 44)
14. g: garden– ghastly, guard (171– 28)
15. h: house– who (237 – 4)
16. i: ink– mystery, pretty, sieve, women, busy, build (421 – 53)
17. i-e: bite – might, style, mild, kind, eider, height, climb
island indict sign (278 – 76)
-y: my – high,pie, rye, buy, I, eye (17 – 14)
18. j: jam/ jog/ jug (0)
jelly, jig – gentle, ginger (18 – 20)
-ge: gorge (0)
-dg: fidget– digit (29 – 11)
19. l: last– llama (1,945 – 1)
20: m: mum– dumb, autumn (1,128 – 19)
21. n: nose– knot, gone, gnome, mnemonic (2,312 – 34)
22. -ng: ring (0)
23. o: on– cough, sausage, gone(357 – 5)
want – wont (19 – 1); quarrel– quod (10 -1)
24. o-e: mole – bowl, roll, soul; old – mould
boast, most, goes, mauve (171 – 100)
-o: no –toe, dough, sew, cocoa, pharaoh, oh, depot (106 – 59)
25. oi: oil– oyster (29 –1)
-oy: toy –buoy (12 – 1)
26. oo (long): food– rude, shrewd, move, group, fruit, truth, tomb,
blue, do, shoe,through, manoeuvre (94 – 108)
27. oo (short): good– would, put, woman, courier (15 -21)
28. or: order– board, court; wart, quart– worn, quorn (188 – 16)
-ore:more – soar, door, four, war, swore,abhor (23– 17)
+ (14 –aw/awe in UK)
29. ou: out– town (74 – 24);
-ow: now – plough (11 – 4)
30. p: pin (0)
31. r: rug– rhubarb, write (1,670 – 27)
32. s: sun – centre,scene (138 – 49)
-ce: face – case; fancy– fantasy (153 – 65)
33. sh: shop – chute, sure, moustache, liquorice (166 – 30)
-tion: ignition– mission, pension, suspicion,fashion (216 – 81)
34. t: tap, pet – pterodactyl, two, debt (1,398 – 4)
--te: delicate – democrat (52 – 3)
35. th (sharp): this (0)
36. th (soft): thing (0)
37. u: up– front, some, couple, blood (308 – 68)
38. u-e: cute – you,newt, neutral, suit, beauty, Tuesday, nuclear (137 – 21)
-ue: cue –few, view,menu (20– 22)
39. v: van (0)
-ve: have –spiv (116– 3) [80 with surplus –e]
-v-: river– chivvy (73 – 7) – v/vv after short vowel
40. w: window– which (216 – 31)
41. y: yak– use (31 – 11)
42. z: zip– xylophone (16 – 1)
-se: rose –froze (85– 33)
wise– size (UK 31 – 3, US 11 – 22)
43. zh: -si-/-su-: vision, measure – azure (20 – 3)
44. Unstressed, unclear vowel sound (or schwa),
occurring mainly in 8 endings and 2 prefixes:
-able: loveable– credible(33 – 17)
-ccle: bundle (2 consonants + -le for -l) (0)
-al: vertical– novel, anvil, petrol (200+ – 32)
-ary: ordinary– machinery, inventory, century,carpentry(37 – 55)
-en: fasten– abandon, truncheon, orphan, goblin, certain (73 – 132)
-ence: absence– balance (33 – 26)
-ent: absent – pleasant (176 – 58)
-er: father –author, armour, nectar, centre, injure,quota (UK 340, US 346 – 135/129)
butcher – picture (42 –ure)
de-: decide – divide (57 – 29)
in-: indulge – endure (73 – 30)
Consonant doubling rule for showing short, stressed vowels
merry (regular) – very(missing) – serrated(surplus)
(503 - 601 - 219)