Short answer: it depends on what you want (highest APY, easy nationwide access, debit card/allowance tools, or long‑term investing). Below are top picks by category and why — with reputable sources you can check for current rates and eligibility.

Best for highest short‑term APY (small balances)

• Regional credit unions and some small banks often pay the biggest APYs for youth accounts (but typically only on the first $500–$1,000). Good examples include Spectra, Spectrum/Chevron FCU, Neighbors CU and others that offer very high APYs on limited balances. These are great if you want your child to see quick growth on a small starter balance. (investopedia.com)

Best overall high‑rate kids’ savings (national/online credit union)

• Alliant Credit Union — strong kids savings APY, no monthly fee if you go paperless, easy parental access and goal accounts (membership is required but can be simple to meet). Good pick if you want a true savings account (NCUA insured) with a solid rate. (alliantcreditunion.org)

Best for easy, nationwide opening with no balance caps

• Capital One Kids Savings (part of Capital One 360) — no monthly fee, no minimum, simple parent/child setup and competitive APY on all balances (good if you expect larger balances over time). This is a convenient, nationwide option. (forbes.com, kiplinger.com)

Best for allowance, parental controls and teaching tools (debit + “savings” features)

• Greenlight and similar fintechs (Step, Acorns Early, etc.) — these provide debit cards for kids, chore/allowance automation, in‑app saving goals and savings rewards (interest or “rewards” that boost balances). They’re excellent for teaching money management, but check monthly fees and whether the “earnings” are true bank interest or rewards. (greenlight.com)

Best if you want long‑term growth / investing (custodial)

• Brokerage custodial accounts (UGMA/UTMA) or teen investing accounts — e.g., Fidelity Youth, Merrill Edge custodial accounts, Vanguard/Schwab custodial accounts — let you invest for decades of growth rather than keep cash in savings. Use these if your goal is college/homedownpayment sized savings and you’re comfortable with market risk. (Note: custodial funds legally become the child’s at the age of majority.) (fidelity.com, bankrate.com)

How to choose (quick checklist)

• APY vs. cap: is the high rate only on the first $500–$1,000? (common). (investopedia.com)
• Fees & minimums: monthly fees or minimum balance requirements reduce earnings. (alliantcreditunion.org)
• Access & control: do you want a joint account, custodial (UGMA/UTMA), or a supervised teen account with a debit card? (fidelity.com, greenlight.com)
• Insurance: bank accounts = FDIC, credit unions = NCUA; custodial brokerage cash may be SIPC‑protected (investments are not FDIC insured). (fidelity.com, alliantcreditunion.org)

Examples (summary)

• High short‑term APY on small balances: Spectra Credit Union, Spectrum/Chevron FCU, select local credit unions. (investopedia.com, cnbc.com)
• Solid nationwide kids savings: Alliant Credit Union (kids savings). (alliantcreditunion.org)
• Easy nationwide/no cap: Capital One Kids Savings (Capital One 360). (forbes.com)
• Teaching & debit card: Greenlight, Step, Acorns Early. (greenlight.com, step.com)
• Long‑term investing for kids: Fidelity Youth, Merrill Edge/Schwab/Vanguard custodial accounts. (fidelity.com, bankrate.com)

Rates and offers change often — if you want, tell me which 2–3 of the above (or any specific banks/credit unions) you’re considering and I’ll pull today’s APYs, fees, minimums and membership/eligibility rules so you can compare side‑by‑side.