Yes. Set Maximum self-reported player level on the Match Settings tab of Rules & Limits. Players choosing their own level in your club can't pick anything above it.
How to set it
Go to Settings → Rules & Limits.
Open the Match Settings tab.
Choose a value in Maximum self-reported player level (from 1.0 to 7.0 in steps of 0.5), or No maximum.
Click Save.
If your club offers both padel and tennis, there is one field per sport: Maximum self-reported padel level and Maximum self-reported tennis level.
What players see
When a player chooses their own level while viewing or booking at your club, the app shows "This club has a limited self-rating of" followed by your limit, and they can't go above it.
Good to know
The limit applies to the level a player chooses themselves. It doesn't stop a padel player's level rising above it through match results.
Staff can still set any level from 1 to 7. See "How do I change a player's level?".